diff --git a/nixos/modules/installer/tools/nixos-rebuild.sh b/nixos/modules/installer/tools/nixos-rebuild.sh
index 8e55a4f525f9..4f73865dad6a 100644
--- a/nixos/modules/installer/tools/nixos-rebuild.sh
+++ b/nixos/modules/installer/tools/nixos-rebuild.sh
@@ -15,6 +15,7 @@ origArgs=("$@")
 extraBuildFlags=()
 action=
 buildNix=1
+fast=
 rollback=
 upgrade=
 repair=
@@ -52,13 +53,13 @@ while [ "$#" -gt 0 ]; do
         repair=1
         extraBuildFlags+=("$i")
         ;;
-      --show-trace|--no-build-hook|--keep-failed|-K|--keep-going|-k|--verbose|-v|-vv|-vvv|-vvvv|-vvvvv|--fallback|--repair|--no-build-output|-Q)
-        extraBuildFlags+=("$i")
-        ;;
       --max-jobs|-j|--cores|-I)
         j="$1"; shift 1
         extraBuildFlags+=("$i" "$j")
         ;;
+      --show-trace|--no-build-hook|--keep-failed|-K|--keep-going|-k|--verbose|-v|-vv|-vvv|-vvvv|-vvvvv|--fallback|--repair|--no-build-output|-Q|-j*)
+        extraBuildFlags+=("$i")
+        ;;
       --option)
         j="$1"; shift 1
         k="$1"; shift 1
@@ -66,6 +67,7 @@ while [ "$#" -gt 0 ]; do
         ;;
       --fast)
         buildNix=
+        fast=1
         extraBuildFlags+=(--show-trace)
         ;;
       --profile-name|-p)
@@ -217,7 +219,7 @@ if [ -z "$_NIXOS_REBUILD_REEXEC" ]; then
 fi
 
 # Re-execute nixos-rebuild from the Nixpkgs tree.
-if [ -z "$_NIXOS_REBUILD_REEXEC" -a -n "$canRun" ]; then
+if [ -z "$_NIXOS_REBUILD_REEXEC" -a -n "$canRun" -a -z "$fast" ]; then
     if p=$(nix-build --no-out-link --expr 'with import <nixpkgs/nixos> {}; config.system.build.nixos-rebuild' "${extraBuildFlags[@]}"); then
         export _NIXOS_REBUILD_REEXEC=1
         exec $p/bin/nixos-rebuild "${origArgs[@]}"