diff --git a/tests/functional/add.sh b/tests/functional/add.sh
old mode 100644
new mode 100755
index a4bb0e225..9b448e33b
--- a/tests/functional/add.sh
+++ b/tests/functional/add.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 path1=$(nix-store --add ./dummy)
diff --git a/tests/functional/bash-profile.sh b/tests/functional/bash-profile.sh
old mode 100644
new mode 100755
index 3faeaaba1..6cfa5bd9c
--- a/tests/functional/bash-profile.sh
+++ b/tests/functional/bash-profile.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 sed -e "s|@localstatedir@|$TEST_ROOT/profile-var|g" -e "s|@coreutils@|$coreutils|g" < ../../scripts/nix-profile.sh.in > $TEST_ROOT/nix-profile.sh
diff --git a/tests/functional/binary-cache-build-remote.sh b/tests/functional/binary-cache-build-remote.sh
old mode 100644
new mode 100755
index 81cd21a4a..0303e9410
--- a/tests/functional/binary-cache-build-remote.sh
+++ b/tests/functional/binary-cache-build-remote.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/binary-cache.sh b/tests/functional/binary-cache.sh
old mode 100644
new mode 100755
index 2a8d5ccdb..54a3687ca
--- a/tests/functional/binary-cache.sh
+++ b/tests/functional/binary-cache.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 needLocalStore "'--no-require-sigs' can’t be used with the daemon"
diff --git a/tests/functional/brotli.sh b/tests/functional/brotli.sh
old mode 100644
new mode 100755
index dc9bbdb66..02a2a0875
--- a/tests/functional/brotli.sh
+++ b/tests/functional/brotli.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/build-delete.sh b/tests/functional/build-delete.sh
old mode 100644
new mode 100755
index 9c56b00e8..2ef3008f6
--- a/tests/functional/build-delete.sh
+++ b/tests/functional/build-delete.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/build-dry.sh b/tests/functional/build-dry.sh
old mode 100644
new mode 100755
index 6d1754af5..9336cf745
--- a/tests/functional/build-dry.sh
+++ b/tests/functional/build-dry.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 ###################################################
diff --git a/tests/functional/build-remote-content-addressed-fixed.sh b/tests/functional/build-remote-content-addressed-fixed.sh
old mode 100644
new mode 100755
diff --git a/tests/functional/build-remote-content-addressed-floating.sh b/tests/functional/build-remote-content-addressed-floating.sh
old mode 100644
new mode 100755
diff --git a/tests/functional/build-remote-input-addressed.sh b/tests/functional/build-remote-input-addressed.sh
old mode 100644
new mode 100755
diff --git a/tests/functional/build-remote-trustless-should-fail-0.sh b/tests/functional/build-remote-trustless-should-fail-0.sh
old mode 100644
new mode 100755
diff --git a/tests/functional/build-remote-trustless-should-pass-0.sh b/tests/functional/build-remote-trustless-should-pass-0.sh
old mode 100644
new mode 100755
diff --git a/tests/functional/build-remote-trustless-should-pass-1.sh b/tests/functional/build-remote-trustless-should-pass-1.sh
old mode 100644
new mode 100755
diff --git a/tests/functional/build-remote-trustless-should-pass-2.sh b/tests/functional/build-remote-trustless-should-pass-2.sh
old mode 100644
new mode 100755
diff --git a/tests/functional/build-remote-trustless-should-pass-3.sh b/tests/functional/build-remote-trustless-should-pass-3.sh
old mode 100644
new mode 100755
diff --git a/tests/functional/build-remote-with-mounted-ssh-ng.sh b/tests/functional/build-remote-with-mounted-ssh-ng.sh
old mode 100644
new mode 100755
diff --git a/tests/functional/build.sh b/tests/functional/build.sh
old mode 100644
new mode 100755
index 95a20dc6a..9fb4357be
--- a/tests/functional/build.sh
+++ b/tests/functional/build.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/case-hack.sh b/tests/functional/case-hack.sh
old mode 100644
new mode 100755
index 61bf9b94b..fbc8242ff
--- a/tests/functional/case-hack.sh
+++ b/tests/functional/case-hack.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/check-refs.sh b/tests/functional/check-refs.sh
old mode 100644
new mode 100755
index 3b587d1e5..2cebdd84d
--- a/tests/functional/check-refs.sh
+++ b/tests/functional/check-refs.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/check-reqs.sh b/tests/functional/check-reqs.sh
old mode 100644
new mode 100755
index 856c94cec..2bcd558fd
--- a/tests/functional/check-reqs.sh
+++ b/tests/functional/check-reqs.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/check.sh b/tests/functional/check.sh
old mode 100644
new mode 100755
index 38883c5d7..efb93eeb0
--- a/tests/functional/check.sh
+++ b/tests/functional/check.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # XXX: This shouldn’t be, but #4813 cause this test to fail
diff --git a/tests/functional/chroot-store.sh b/tests/functional/chroot-store.sh
old mode 100644
new mode 100755
index 9e589d04b..60b9c50a7
--- a/tests/functional/chroot-store.sh
+++ b/tests/functional/chroot-store.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 echo example > $TEST_ROOT/example.txt
diff --git a/tests/functional/completions.sh b/tests/functional/completions.sh
old mode 100644
new mode 100755
index d3d5bbd48..9164c5013
--- a/tests/functional/completions.sh
+++ b/tests/functional/completions.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 cd "$TEST_ROOT"
diff --git a/tests/functional/compression-levels.sh b/tests/functional/compression-levels.sh
old mode 100644
new mode 100755
index 85f12974a..34f66c531
--- a/tests/functional/compression-levels.sh
+++ b/tests/functional/compression-levels.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/compute-levels.sh b/tests/functional/compute-levels.sh
old mode 100644
new mode 100755
index de3da2ebd..a8bd27610
--- a/tests/functional/compute-levels.sh
+++ b/tests/functional/compute-levels.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 if [[ $(uname -ms) = "Linux x86_64" ]]; then
diff --git a/tests/functional/config.sh b/tests/functional/config.sh
old mode 100644
new mode 100755
index efdafa8ca..1811b755c
--- a/tests/functional/config.sh
+++ b/tests/functional/config.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Isolate the home for this test.
diff --git a/tests/functional/db-migration.sh b/tests/functional/db-migration.sh
old mode 100644
new mode 100755
index 44cd16bc0..a6a5c7744
--- a/tests/functional/db-migration.sh
+++ b/tests/functional/db-migration.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test that we can successfully migrate from an older db schema
 
 source common.sh
diff --git a/tests/functional/debugger.sh b/tests/functional/debugger.sh
old mode 100644
new mode 100755
index 63d88cbf3..47e644bb7
--- a/tests/functional/debugger.sh
+++ b/tests/functional/debugger.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/dependencies.sh b/tests/functional/dependencies.sh
old mode 100644
new mode 100755
index b93dacac0..5922a1f98
--- a/tests/functional/dependencies.sh
+++ b/tests/functional/dependencies.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/derivation-json.sh b/tests/functional/derivation-json.sh
old mode 100644
new mode 100755
index b6be5d977..59c77e6c5
--- a/tests/functional/derivation-json.sh
+++ b/tests/functional/derivation-json.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 drvPath=$(nix-instantiate simple.nix)
diff --git a/tests/functional/dump-db.sh b/tests/functional/dump-db.sh
old mode 100644
new mode 100755
index 48647f403..2d0460275
--- a/tests/functional/dump-db.sh
+++ b/tests/functional/dump-db.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 needLocalStore "--dump-db requires a local store"
diff --git a/tests/functional/eval-store.sh b/tests/functional/eval-store.sh
old mode 100644
new mode 100755
index 9937ecbce..0ab608acc
--- a/tests/functional/eval-store.sh
+++ b/tests/functional/eval-store.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Using `--eval-store` with the daemon will eventually copy everything
diff --git a/tests/functional/eval.sh b/tests/functional/eval.sh
old mode 100644
new mode 100755
index 502170d14..acd6e2915
--- a/tests/functional/eval.sh
+++ b/tests/functional/eval.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/experimental-features.sh b/tests/functional/experimental-features.sh
old mode 100644
new mode 100755
index 12112b293..38f198eee
--- a/tests/functional/experimental-features.sh
+++ b/tests/functional/experimental-features.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Skipping these two for now, because we actually *do* want flags and
diff --git a/tests/functional/export-graph.sh b/tests/functional/export-graph.sh
old mode 100644
new mode 100755
index 1f6232a40..281b5b05b
--- a/tests/functional/export-graph.sh
+++ b/tests/functional/export-graph.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/export.sh b/tests/functional/export.sh
old mode 100644
new mode 100755
index 2238539bc..fce2e333a
--- a/tests/functional/export.sh
+++ b/tests/functional/export.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/extra-sandbox-profile.sh b/tests/functional/extra-sandbox-profile.sh
old mode 100644
new mode 100755
index ac3ca036f..672e5779d
--- a/tests/functional/extra-sandbox-profile.sh
+++ b/tests/functional/extra-sandbox-profile.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 if [[ $(uname) != Darwin ]]; then skipTest "Need Darwin"; fi
diff --git a/tests/functional/fetchClosure.sh b/tests/functional/fetchClosure.sh
old mode 100644
new mode 100755
index a02d1ce7a..4026b0790
--- a/tests/functional/fetchClosure.sh
+++ b/tests/functional/fetchClosure.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 enableFeatures "fetch-closure"
diff --git a/tests/functional/fetchGit.sh b/tests/functional/fetchGit.sh
old mode 100644
new mode 100755
index 74d6de4e3..d89d59a81
--- a/tests/functional/fetchGit.sh
+++ b/tests/functional/fetchGit.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireGit
diff --git a/tests/functional/fetchGitRefs.sh b/tests/functional/fetchGitRefs.sh
old mode 100644
new mode 100755
index d643fea04..b17cc2090
--- a/tests/functional/fetchGitRefs.sh
+++ b/tests/functional/fetchGitRefs.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireGit
diff --git a/tests/functional/fetchGitSubmodules.sh b/tests/functional/fetchGitSubmodules.sh
old mode 100644
new mode 100755
index bd82a0a17..7c5f7b0d6
--- a/tests/functional/fetchGitSubmodules.sh
+++ b/tests/functional/fetchGitSubmodules.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 set -u
diff --git a/tests/functional/fetchGitVerification.sh b/tests/functional/fetchGitVerification.sh
old mode 100644
new mode 100755
index b80e061b5..27f9a8cf5
--- a/tests/functional/fetchGitVerification.sh
+++ b/tests/functional/fetchGitVerification.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireGit
diff --git a/tests/functional/fetchMercurial.sh b/tests/functional/fetchMercurial.sh
old mode 100644
new mode 100755
index 9f7cef7b2..f3774fc74
--- a/tests/functional/fetchMercurial.sh
+++ b/tests/functional/fetchMercurial.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 [[ $(type -p hg) ]] || skipTest "Mercurial not installed"
diff --git a/tests/functional/fetchPath.sh b/tests/functional/fetchPath.sh
old mode 100644
new mode 100755
index 29be38ce2..e466e4494
--- a/tests/functional/fetchPath.sh
+++ b/tests/functional/fetchPath.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 touch $TEST_ROOT/foo -t 202211111111
diff --git a/tests/functional/fetchTree-file.sh b/tests/functional/fetchTree-file.sh
old mode 100644
new mode 100755
index be698ea35..9c9532876
--- a/tests/functional/fetchTree-file.sh
+++ b/tests/functional/fetchTree-file.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/fetchurl.sh b/tests/functional/fetchurl.sh
old mode 100644
new mode 100755
index a3620f52b..2255dbbdc
--- a/tests/functional/fetchurl.sh
+++ b/tests/functional/fetchurl.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/filter-source.sh b/tests/functional/filter-source.sh
old mode 100644
new mode 100755
index ba34d2eac..c5e10be93
--- a/tests/functional/filter-source.sh
+++ b/tests/functional/filter-source.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 rm -rf $TEST_ROOT/filterin
diff --git a/tests/functional/fixed.sh b/tests/functional/fixed.sh
old mode 100644
new mode 100755
index 7bbecda91..4d07d00cd
--- a/tests/functional/fixed.sh
+++ b/tests/functional/fixed.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/flakes/absolute-attr-paths.sh b/tests/functional/flakes/absolute-attr-paths.sh
old mode 100644
new mode 100755
index 491adceb7..8ed1755c4
--- a/tests/functional/flakes/absolute-attr-paths.sh
+++ b/tests/functional/flakes/absolute-attr-paths.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 flake1Dir=$TEST_ROOT/flake1
diff --git a/tests/functional/flakes/absolute-paths.sh b/tests/functional/flakes/absolute-paths.sh
old mode 100644
new mode 100755
index e7bfba12d..a355a7a1c
--- a/tests/functional/flakes/absolute-paths.sh
+++ b/tests/functional/flakes/absolute-paths.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireGit
diff --git a/tests/functional/flakes/build-paths.sh b/tests/functional/flakes/build-paths.sh
old mode 100644
new mode 100755
index 4e5c68095..a336471f0
--- a/tests/functional/flakes/build-paths.sh
+++ b/tests/functional/flakes/build-paths.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 flake1Dir=$TEST_ROOT/flake1
diff --git a/tests/functional/flakes/bundle.sh b/tests/functional/flakes/bundle.sh
old mode 100644
new mode 100755
index 67bbb05ac..711691e0b
--- a/tests/functional/flakes/bundle.sh
+++ b/tests/functional/flakes/bundle.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 cp ../simple.nix ../simple.builder.sh ../config.nix $TEST_HOME
diff --git a/tests/functional/flakes/check.sh b/tests/functional/flakes/check.sh
old mode 100644
new mode 100755
index 0433e5335..3b83dcafe
--- a/tests/functional/flakes/check.sh
+++ b/tests/functional/flakes/check.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 flakeDir=$TEST_ROOT/flake3
diff --git a/tests/functional/flakes/circular.sh b/tests/functional/flakes/circular.sh
old mode 100644
new mode 100755
index d3bb8e8a3..6cab3a72b
--- a/tests/functional/flakes/circular.sh
+++ b/tests/functional/flakes/circular.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test circular flake dependencies.
 source ./common.sh
 
diff --git a/tests/functional/flakes/config.sh b/tests/functional/flakes/config.sh
old mode 100644
new mode 100755
index d1941a6be..66b917457
--- a/tests/functional/flakes/config.sh
+++ b/tests/functional/flakes/config.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 cp ../simple.nix ../simple.builder.sh ../config.nix $TEST_HOME
diff --git a/tests/functional/flakes/develop.sh b/tests/functional/flakes/develop.sh
old mode 100644
new mode 100755
index e1e53d364..83be2e308
--- a/tests/functional/flakes/develop.sh
+++ b/tests/functional/flakes/develop.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ../common.sh
 
 clearStore
diff --git a/tests/functional/flakes/flake-in-submodule.sh b/tests/functional/flakes/flake-in-submodule.sh
old mode 100644
new mode 100755
index 85a4d3389..2988352a9
--- a/tests/functional/flakes/flake-in-submodule.sh
+++ b/tests/functional/flakes/flake-in-submodule.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Tests that:
diff --git a/tests/functional/flakes/flakes.sh b/tests/functional/flakes/flakes.sh
old mode 100644
new mode 100755
index 35b0c5d84..3057c0293
--- a/tests/functional/flakes/flakes.sh
+++ b/tests/functional/flakes/flakes.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireGit
diff --git a/tests/functional/flakes/follow-paths.sh b/tests/functional/flakes/follow-paths.sh
old mode 100644
new mode 100755
index 1afd91bd2..ea56b9503
--- a/tests/functional/flakes/follow-paths.sh
+++ b/tests/functional/flakes/follow-paths.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireGit
diff --git a/tests/functional/flakes/init.sh b/tests/functional/flakes/init.sh
old mode 100644
new mode 100755
index 2d4c77ba1..f8d51e819
--- a/tests/functional/flakes/init.sh
+++ b/tests/functional/flakes/init.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireGit
diff --git a/tests/functional/flakes/inputs.sh b/tests/functional/flakes/inputs.sh
old mode 100644
new mode 100755
index 80620488a..0327a3e9e
--- a/tests/functional/flakes/inputs.sh
+++ b/tests/functional/flakes/inputs.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireGit
diff --git a/tests/functional/flakes/mercurial.sh b/tests/functional/flakes/mercurial.sh
old mode 100644
new mode 100755
index 7074af6f7..0e9f2d626
--- a/tests/functional/flakes/mercurial.sh
+++ b/tests/functional/flakes/mercurial.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 [[ $(type -p hg) ]] || skipTest "Mercurial not installed"
diff --git a/tests/functional/flakes/prefetch.sh b/tests/functional/flakes/prefetch.sh
old mode 100644
new mode 100755
index bfd0533f9..a451b7120
--- a/tests/functional/flakes/prefetch.sh
+++ b/tests/functional/flakes/prefetch.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Test symlinks in zip files (#10649).
diff --git a/tests/functional/flakes/run.sh b/tests/functional/flakes/run.sh
old mode 100644
new mode 100755
index 9fa51d1c7..4d8b512b9
--- a/tests/functional/flakes/run.sh
+++ b/tests/functional/flakes/run.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ../common.sh
 
 clearStore
diff --git a/tests/functional/flakes/search-root.sh b/tests/functional/flakes/search-root.sh
old mode 100644
new mode 100755
index 6b137aa86..c2337edc0
--- a/tests/functional/flakes/search-root.sh
+++ b/tests/functional/flakes/search-root.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/flakes/show.sh b/tests/functional/flakes/show.sh
old mode 100644
new mode 100755
index a3d300552..22e1f4193
--- a/tests/functional/flakes/show.sh
+++ b/tests/functional/flakes/show.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 flakeDir=$TEST_ROOT/flake
diff --git a/tests/functional/flakes/unlocked-override.sh b/tests/functional/flakes/unlocked-override.sh
old mode 100644
new mode 100755
index 8abc8b7d3..680a1505c
--- a/tests/functional/flakes/unlocked-override.sh
+++ b/tests/functional/flakes/unlocked-override.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 requireGit
diff --git a/tests/functional/fmt.sh b/tests/functional/fmt.sh
old mode 100644
new mode 100755
index 3c1bd9989..8fc9a3979
--- a/tests/functional/fmt.sh
+++ b/tests/functional/fmt.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/function-trace.sh b/tests/functional/function-trace.sh
index bd804bf18..71f18b67f 100755
--- a/tests/functional/function-trace.sh
+++ b/tests/functional/function-trace.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 set +x
diff --git a/tests/functional/gc-auto.sh b/tests/functional/gc-auto.sh
old mode 100644
new mode 100755
index 281eef20d..98bb7e60e
--- a/tests/functional/gc-auto.sh
+++ b/tests/functional/gc-auto.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 needLocalStore "“min-free” and “max-free” are daemon options"
diff --git a/tests/functional/gc-concurrent.sh b/tests/functional/gc-concurrent.sh
old mode 100644
new mode 100755
index 2c6622c62..67ea3dc74
--- a/tests/functional/gc-concurrent.sh
+++ b/tests/functional/gc-concurrent.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/gc-non-blocking.sh b/tests/functional/gc-non-blocking.sh
old mode 100644
new mode 100755
index ec280badb..ecfa421fb
--- a/tests/functional/gc-non-blocking.sh
+++ b/tests/functional/gc-non-blocking.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test whether the collector is non-blocking, i.e. a build can run in
 # parallel with it.
 source common.sh
diff --git a/tests/functional/gc-runtime.sh b/tests/functional/gc-runtime.sh
old mode 100644
new mode 100755
index dc1826a55..2ee72b61e
--- a/tests/functional/gc-runtime.sh
+++ b/tests/functional/gc-runtime.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 case $system in
diff --git a/tests/functional/gc.sh b/tests/functional/gc.sh
old mode 100644
new mode 100755
index ad09a8b39..1f216ebc7
--- a/tests/functional/gc.sh
+++ b/tests/functional/gc.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/hash-convert.sh b/tests/functional/hash-convert.sh
old mode 100644
new mode 100755
index 9b3afc10b..3a099950f
--- a/tests/functional/hash-convert.sh
+++ b/tests/functional/hash-convert.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Conversion with `nix hash` `nix-hash` and `nix hash convert`
diff --git a/tests/functional/hash-path.sh b/tests/functional/hash-path.sh
old mode 100644
new mode 100755
index 4ad9f8ff2..12605ef71
--- a/tests/functional/hash-path.sh
+++ b/tests/functional/hash-path.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 try () {
diff --git a/tests/functional/help.sh b/tests/functional/help.sh
old mode 100644
new mode 100755
index 868f5d2e9..6436fb500
--- a/tests/functional/help.sh
+++ b/tests/functional/help.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/import-derivation.sh b/tests/functional/import-derivation.sh
old mode 100644
new mode 100755
index 98d61ef49..53efa1f5d
--- a/tests/functional/import-derivation.sh
+++ b/tests/functional/import-derivation.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/impure-derivations.sh b/tests/functional/impure-derivations.sh
old mode 100644
new mode 100755
index 54ed6f5dd..b59f73c77
--- a/tests/functional/impure-derivations.sh
+++ b/tests/functional/impure-derivations.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireDaemonNewerThan "2.8pre20220311"
diff --git a/tests/functional/impure-env.sh b/tests/functional/impure-env.sh
old mode 100644
new mode 100755
index cfea4cae9..3c7df169e
--- a/tests/functional/impure-env.sh
+++ b/tests/functional/impure-env.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Needs the config option 'impure-env' to work
diff --git a/tests/functional/impure-eval.sh b/tests/functional/impure-eval.sh
old mode 100644
new mode 100755
index 6c72f01d7..33a5ea409
--- a/tests/functional/impure-eval.sh
+++ b/tests/functional/impure-eval.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 export REMOTE_STORE="dummy://"
diff --git a/tests/functional/lang-test-infra.sh b/tests/functional/lang-test-infra.sh
old mode 100644
new mode 100755
index 30da8977b..f32ccef05
--- a/tests/functional/lang-test-infra.sh
+++ b/tests/functional/lang-test-infra.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test the function for lang.sh
 source common.sh
 
diff --git a/tests/functional/lang.sh b/tests/functional/lang.sh
index 60603cebe..a853cfd81 100755
--- a/tests/functional/lang.sh
+++ b/tests/functional/lang.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 set -o pipefail
diff --git a/tests/functional/legacy-ssh-store.sh b/tests/functional/legacy-ssh-store.sh
old mode 100644
new mode 100755
index 56b4c2d20..3a1a7b022
--- a/tests/functional/legacy-ssh-store.sh
+++ b/tests/functional/legacy-ssh-store.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 store_uri="ssh://localhost?remote-store=$TEST_ROOT/other-store"
diff --git a/tests/functional/linux-sandbox.sh b/tests/functional/linux-sandbox.sh
old mode 100644
new mode 100755
index e553791d9..e71224f5e
--- a/tests/functional/linux-sandbox.sh
+++ b/tests/functional/linux-sandbox.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 needLocalStore "the sandbox only runs on the builder side, so it makes no sense to test it with the daemon"
diff --git a/tests/functional/logging.sh b/tests/functional/logging.sh
old mode 100644
new mode 100755
index 1ccc21d0b..63752f6db
--- a/tests/functional/logging.sh
+++ b/tests/functional/logging.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/misc.sh b/tests/functional/misc.sh
old mode 100644
new mode 100755
index d4379b7ce..9eb80ad22
--- a/tests/functional/misc.sh
+++ b/tests/functional/misc.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # Tests miscellaneous commands.
diff --git a/tests/functional/multiple-outputs.sh b/tests/functional/multiple-outputs.sh
old mode 100644
new mode 100755
index 330600d08..af9f8af72
--- a/tests/functional/multiple-outputs.sh
+++ b/tests/functional/multiple-outputs.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/nar-access.sh b/tests/functional/nar-access.sh
old mode 100644
new mode 100755
index 87981e7d9..8839fd043
--- a/tests/functional/nar-access.sh
+++ b/tests/functional/nar-access.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 echo "building test path"
diff --git a/tests/functional/nested-sandboxing.sh b/tests/functional/nested-sandboxing.sh
old mode 100644
new mode 100755
index 61fe043c6..44c3bb2bc
--- a/tests/functional/nested-sandboxing.sh
+++ b/tests/functional/nested-sandboxing.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 # This test is run by `tests/functional/nested-sandboxing/runner.nix` in an extra layer of sandboxing.
 [[ -d /nix/store ]] || skipTest "running this test without Nix's deps being drawn from /nix/store is not yet supported"
diff --git a/tests/functional/nix-build.sh b/tests/functional/nix-build.sh
old mode 100644
new mode 100755
index 44a5a14cd..45ff314c7
--- a/tests/functional/nix-build.sh
+++ b/tests/functional/nix-build.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/nix-channel.sh b/tests/functional/nix-channel.sh
old mode 100644
new mode 100755
index ca5df3bdd..a4870e7a8
--- a/tests/functional/nix-channel.sh
+++ b/tests/functional/nix-channel.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearProfiles
diff --git a/tests/functional/nix-collect-garbage-d.sh b/tests/functional/nix-collect-garbage-d.sh
old mode 100644
new mode 100755
index bf30f8938..07aaf61e9
--- a/tests/functional/nix-collect-garbage-d.sh
+++ b/tests/functional/nix-collect-garbage-d.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/nix-copy-ssh-ng.sh b/tests/functional/nix-copy-ssh-ng.sh
old mode 100644
new mode 100755
index 62e99cd24..1fd735b9d
--- a/tests/functional/nix-copy-ssh-ng.sh
+++ b/tests/functional/nix-copy-ssh-ng.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 source nix-copy-ssh-common.sh "ssh-ng"
diff --git a/tests/functional/nix-copy-ssh.sh b/tests/functional/nix-copy-ssh.sh
old mode 100644
new mode 100755
index 12e8346bc..1dc256e49
--- a/tests/functional/nix-copy-ssh.sh
+++ b/tests/functional/nix-copy-ssh.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 source nix-copy-ssh-common.sh "ssh"
diff --git a/tests/functional/nix-profile.sh b/tests/functional/nix-profile.sh
old mode 100644
new mode 100755
index 7c4da6283..3e5846cf2
--- a/tests/functional/nix-profile.sh
+++ b/tests/functional/nix-profile.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/nix-shell.sh b/tests/functional/nix-shell.sh
old mode 100644
new mode 100755
index 04c83138e..c38107e64
--- a/tests/functional/nix-shell.sh
+++ b/tests/functional/nix-shell.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/nix_path.sh b/tests/functional/nix_path.sh
old mode 100644
new mode 100755
index 2b222b4a1..e6a2193f3
--- a/tests/functional/nix_path.sh
+++ b/tests/functional/nix_path.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Regression for https://github.com/NixOS/nix/issues/5998 and https://github.com/NixOS/nix/issues/5980
 
 source common.sh
diff --git a/tests/functional/optimise-store.sh b/tests/functional/optimise-store.sh
old mode 100644
new mode 100755
index 8c2d05cd5..70ce954f9
--- a/tests/functional/optimise-store.sh
+++ b/tests/functional/optimise-store.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/output-normalization.sh b/tests/functional/output-normalization.sh
old mode 100644
new mode 100755
index 0f6df5e31..2b319201a
--- a/tests/functional/output-normalization.sh
+++ b/tests/functional/output-normalization.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 testNormalization () {
diff --git a/tests/functional/pass-as-file.sh b/tests/functional/pass-as-file.sh
old mode 100644
new mode 100755
index 2c0bc5031..21d9ffc6d
--- a/tests/functional/pass-as-file.sh
+++ b/tests/functional/pass-as-file.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/path-from-hash-part.sh b/tests/functional/path-from-hash-part.sh
old mode 100644
new mode 100755
index bdd104434..41d1b7410
--- a/tests/functional/path-from-hash-part.sh
+++ b/tests/functional/path-from-hash-part.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 path=$(nix build --no-link --print-out-paths -f simple.nix)
diff --git a/tests/functional/path-info.sh b/tests/functional/path-info.sh
old mode 100644
new mode 100755
index 763935eb7..8597de683
--- a/tests/functional/path-info.sh
+++ b/tests/functional/path-info.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 echo foo > $TEST_ROOT/foo
diff --git a/tests/functional/placeholders.sh b/tests/functional/placeholders.sh
old mode 100644
new mode 100755
index cd1bb7bc2..f2b8bf6bf
--- a/tests/functional/placeholders.sh
+++ b/tests/functional/placeholders.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/plugins.sh b/tests/functional/plugins.sh
old mode 100644
new mode 100755
index baf71a362..ab4876df9
--- a/tests/functional/plugins.sh
+++ b/tests/functional/plugins.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 if [[ $BUILD_SHARED_LIBS != 1 ]]; then
diff --git a/tests/functional/post-hook.sh b/tests/functional/post-hook.sh
old mode 100644
new mode 100755
index 752f8220c..c0b1ab3aa
--- a/tests/functional/post-hook.sh
+++ b/tests/functional/post-hook.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/pure-eval.sh b/tests/functional/pure-eval.sh
old mode 100644
new mode 100755
index 5334bf28e..6d8aa35ec
--- a/tests/functional/pure-eval.sh
+++ b/tests/functional/pure-eval.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/read-only-store.sh b/tests/functional/read-only-store.sh
old mode 100644
new mode 100755
index 834ac1b51..ecc57642d
--- a/tests/functional/read-only-store.sh
+++ b/tests/functional/read-only-store.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 enableFeatures "read-only-local-store"
diff --git a/tests/functional/readfile-context.sh b/tests/functional/readfile-context.sh
old mode 100644
new mode 100755
index 31e70ddb1..76fad9349
--- a/tests/functional/readfile-context.sh
+++ b/tests/functional/readfile-context.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/recursive.sh b/tests/functional/recursive.sh
old mode 100644
new mode 100755
index 0bf00f8fa..a9966aabd
--- a/tests/functional/recursive.sh
+++ b/tests/functional/recursive.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 enableFeatures 'recursive-nix'
diff --git a/tests/functional/referrers.sh b/tests/functional/referrers.sh
old mode 100644
new mode 100755
index 81323c280..898032e42
--- a/tests/functional/referrers.sh
+++ b/tests/functional/referrers.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 needLocalStore "uses some low-level store manipulations that aren’t available through the daemon"
diff --git a/tests/functional/remote-store.sh b/tests/functional/remote-store.sh
old mode 100644
new mode 100755
index e2c16f18a..171a5d391
--- a/tests/functional/remote-store.sh
+++ b/tests/functional/remote-store.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/repair.sh b/tests/functional/repair.sh
old mode 100644
new mode 100755
index c8f07b1c6..552e04280
--- a/tests/functional/repair.sh
+++ b/tests/functional/repair.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 needLocalStore "--repair needs a local store"
diff --git a/tests/functional/repl.sh b/tests/functional/repl.sh
old mode 100644
new mode 100755
index 222145a7a..fca982807
--- a/tests/functional/repl.sh
+++ b/tests/functional/repl.sh
@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+
 source common.sh
 
 testDir="$PWD"
diff --git a/tests/functional/restricted.sh b/tests/functional/restricted.sh
old mode 100644
new mode 100755
index 3de26eb36..ab4cad5cf
--- a/tests/functional/restricted.sh
+++ b/tests/functional/restricted.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/search.sh b/tests/functional/search.sh
old mode 100644
new mode 100755
index d9c7a75da..ce17411d2
--- a/tests/functional/search.sh
+++ b/tests/functional/search.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/secure-drv-outputs.sh b/tests/functional/secure-drv-outputs.sh
old mode 100644
new mode 100755
index 50a9c4428..7d81db58b
--- a/tests/functional/secure-drv-outputs.sh
+++ b/tests/functional/secure-drv-outputs.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test that users cannot register specially-crafted derivations that
 # produce output paths belonging to other derivations.  This could be
 # used to inject malware into the store.
diff --git a/tests/functional/selfref-gc.sh b/tests/functional/selfref-gc.sh
old mode 100644
new mode 100755
index 3f1f50eea..37ce33089
--- a/tests/functional/selfref-gc.sh
+++ b/tests/functional/selfref-gc.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireDaemonNewerThan "2.6.0pre20211215"
diff --git a/tests/functional/shell.sh b/tests/functional/shell.sh
old mode 100644
new mode 100755
index 8a3fef3e7..e6bb4b161
--- a/tests/functional/shell.sh
+++ b/tests/functional/shell.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/signing.sh b/tests/functional/signing.sh
old mode 100644
new mode 100755
index 942b51630..bcbd3b675
--- a/tests/functional/signing.sh
+++ b/tests/functional/signing.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/simple.sh b/tests/functional/simple.sh
old mode 100644
new mode 100755
index 50d44f93f..846738cbd
--- a/tests/functional/simple.sh
+++ b/tests/functional/simple.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 drvPath=$(nix-instantiate simple.nix)
diff --git a/tests/functional/ssh-relay.sh b/tests/functional/ssh-relay.sh
old mode 100644
new mode 100755
index 053b2f00d..059c66434
--- a/tests/functional/ssh-relay.sh
+++ b/tests/functional/ssh-relay.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 echo foo > $TEST_ROOT/hello.sh
diff --git a/tests/functional/store-info.sh b/tests/functional/store-info.sh
old mode 100644
new mode 100755
index 18a8131a9..2398f5beb
--- a/tests/functional/store-info.sh
+++ b/tests/functional/store-info.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 STORE_INFO=$(nix store info 2>&1)
diff --git a/tests/functional/structured-attrs.sh b/tests/functional/structured-attrs.sh
old mode 100644
new mode 100755
index 6711efbb4..ba7f5967e
--- a/tests/functional/structured-attrs.sh
+++ b/tests/functional/structured-attrs.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 # 27ce722638 required some incompatible changes to the nix file, so skip this
diff --git a/tests/functional/substitute-with-invalid-ca.sh b/tests/functional/substitute-with-invalid-ca.sh
old mode 100644
new mode 100755
index 4d0b01e0f..d8af67237
--- a/tests/functional/substitute-with-invalid-ca.sh
+++ b/tests/functional/substitute-with-invalid-ca.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 BINARY_CACHE=file://$cacheDir
diff --git a/tests/functional/suggestions.sh b/tests/functional/suggestions.sh
old mode 100644
new mode 100755
index f18fefef9..6ec1cd322
--- a/tests/functional/suggestions.sh
+++ b/tests/functional/suggestions.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/supplementary-groups.sh b/tests/functional/supplementary-groups.sh
old mode 100644
new mode 100755
index d18fb2414..9d474219f
--- a/tests/functional/supplementary-groups.sh
+++ b/tests/functional/supplementary-groups.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 requireSandboxSupport
diff --git a/tests/functional/tarball.sh b/tests/functional/tarball.sh
old mode 100644
new mode 100755
index 062f27ad6..ce162ddce
--- a/tests/functional/tarball.sh
+++ b/tests/functional/tarball.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/test-infra.sh b/tests/functional/test-infra.sh
old mode 100644
new mode 100755
index 54ae120e7..37322b356
--- a/tests/functional/test-infra.sh
+++ b/tests/functional/test-infra.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test the functions for testing themselves!
 # Also test some assumptions on how bash works that they rely on.
 source common.sh
diff --git a/tests/functional/test-libstoreconsumer.sh b/tests/functional/test-libstoreconsumer.sh
old mode 100644
new mode 100755
index 8a77cf5a1..d1a1accb6
--- a/tests/functional/test-libstoreconsumer.sh
+++ b/tests/functional/test-libstoreconsumer.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 drv="$(nix-instantiate simple.nix)"
diff --git a/tests/functional/timeout.sh b/tests/functional/timeout.sh
old mode 100644
new mode 100755
index b179b79a2..441c83b0e
--- a/tests/functional/timeout.sh
+++ b/tests/functional/timeout.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test the `--timeout' option.
 
 source common.sh
diff --git a/tests/functional/toString-path.sh b/tests/functional/toString-path.sh
old mode 100644
new mode 100755
index 07eb87465..d790109f4
--- a/tests/functional/toString-path.sh
+++ b/tests/functional/toString-path.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 mkdir -p $TEST_ROOT/foo
diff --git a/tests/functional/user-envs-migration.sh b/tests/functional/user-envs-migration.sh
old mode 100644
new mode 100755
index 187372b16..992586b95
--- a/tests/functional/user-envs-migration.sh
+++ b/tests/functional/user-envs-migration.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 # Test that the migration of user environments
 # (https://github.com/NixOS/nix/pull/5226) does preserve everything
 
diff --git a/tests/functional/user-envs.sh b/tests/functional/user-envs.sh
old mode 100644
new mode 100755
index a849d5439..ec9d036f8
--- a/tests/functional/user-envs.sh
+++ b/tests/functional/user-envs.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source ./common.sh
 
 source ./user-envs-test-case.sh
diff --git a/tests/functional/why-depends.sh b/tests/functional/why-depends.sh
old mode 100644
new mode 100755
index 9680bf80e..69b365069
--- a/tests/functional/why-depends.sh
+++ b/tests/functional/why-depends.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore
diff --git a/tests/functional/zstd.sh b/tests/functional/zstd.sh
old mode 100644
new mode 100755
index ba7c20501..3bf9d5601
--- a/tests/functional/zstd.sh
+++ b/tests/functional/zstd.sh
@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 source common.sh
 
 clearStore