diff --git a/pkgs/development/haskell-modules/generic-builder.nix b/pkgs/development/haskell-modules/generic-builder.nix
index e097fd5af33e..a8da63493a43 100644
--- a/pkgs/development/haskell-modules/generic-builder.nix
+++ b/pkgs/development/haskell-modules/generic-builder.nix
@@ -211,7 +211,7 @@ stdenv.mkDerivation ({
     configureFlags="${concatStringsSep " " defaultConfigureFlags} $configureFlags"
 
     # nativePkgs defined in stdenv/setup.hs
-    for p in $nativePkgs; do
+    for p in "''${!nativePkgs[@]}"; do
       if [ -d "$p/lib/${ghc.name}/package.conf.d" ]; then
         cp -f "$p/lib/${ghc.name}/package.conf.d/"*.conf $packageConfDir/
         continue
diff --git a/pkgs/development/interpreters/python/wrap.sh b/pkgs/development/interpreters/python/wrap.sh
index 1c74e612b559..4b9b2024981a 100644
--- a/pkgs/development/interpreters/python/wrap.sh
+++ b/pkgs/development/interpreters/python/wrap.sh
@@ -86,7 +86,7 @@ wrapPythonProgramsIn() {
 _addToPythonPath() {
     local dir="$1"
     # Stop if we've already visited here.
-    if [ -n "${pythonPathsSeen[$dir]}" ]; then return; fi
+    [ -n "${pythonPathsSeen[$dir]}" ] || return 0
     pythonPathsSeen[$dir]=1
     # addToSearchPath is defined in stdenv/generic/setup.sh. It will have
     # the effect of calling `export program_X=$dir/...:$program_X`.
diff --git a/pkgs/servers/x11/xorg/builder.sh b/pkgs/servers/x11/xorg/builder.sh
index 055886374df4..3a8cf6fa6c8e 100644
--- a/pkgs/servers/x11/xorg/builder.sh
+++ b/pkgs/servers/x11/xorg/builder.sh
@@ -18,14 +18,14 @@ postInstall() {
 
     for r in $requires; do
         if test -n "$crossConfig"; then
-            for p in $crossPkgs; do
+            for p in "${!crossPkgs[@]}"; do
                 if test -e $p/lib/pkgconfig/$r.pc; then
                     echo "  found requisite $r in $p"
                     propagatedBuildInputs="$propagatedBuildInputs $p"
                 fi
             done
         else
-            for p in $nativePkgs; do
+            for p in "${!nativePkgs[@]}"; do
                 if test -e $p/lib/pkgconfig/$r.pc; then
                     echo "  found requisite $r in $p"
                     propagatedNativeBuildInputs="$propagatedNativeBuildInputs $p"
diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index de94565ed6d7..e90c7e03473b 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -275,17 +275,14 @@ runHook addInputsHook
 
 # Recursively find all build inputs.
 findInputs() {
-    local pkg="$1"
+    local pkg=$1
     local var=$2
+    local -n varDeref=$var
     local propagatedBuildInputsFile=$3
 
-    case ${!var} in
-        *\ $pkg\ *)
-            return 0
-            ;;
-    esac
-
-    eval $var="'${!var} $pkg '"
+    # Stop if we've already added this one
+    [[ -z "${varDeref["$pkg"]}" ]] || return 0
+    varDeref["$pkg"]=1
 
     if ! [ -e "$pkg" ]; then
         echo "build input $pkg does not exist" >&2
@@ -296,8 +293,8 @@ findInputs() {
         source "$pkg"
     fi
 
-    if [ -d $1/bin ]; then
-        addToSearchPath _PATH $1/bin
+    if [ -d "$pkg/bin" ]; then
+        addToSearchPath _PATH "$pkg/bin"
     fi
 
     if [ -f "$pkg/nix-support/setup-hook" ]; then
@@ -317,19 +314,19 @@ findInputs() {
 if [ -z "$crossConfig" ]; then
     # Not cross-compiling - both buildInputs (and variants like propagatedBuildInputs)
     # are handled identically to nativeBuildInputs
-    nativePkgs=""
+    declare -gA nativePkgs
     for i in $nativeBuildInputs $buildInputs \
              $defaultNativeBuildInputs $defaultBuildInputs \
              $propagatedNativeBuildInputs $propagatedBuildInputs; do
         findInputs $i nativePkgs propagated-native-build-inputs
     done
 else
-    crossPkgs=""
+    declare -gA crossPkgs
     for i in $buildInputs $defaultBuildInputs $propagatedBuildInputs; do
         findInputs $i crossPkgs propagated-build-inputs
     done
 
-    nativePkgs=""
+    declare -gA nativePkgs
     for i in $nativeBuildInputs $defaultNativeBuildInputs $propagatedNativeBuildInputs; do
         findInputs $i nativePkgs propagated-native-build-inputs
     done
@@ -345,7 +342,7 @@ _addToNativeEnv() {
     runHook envHook "$pkg"
 }
 
-for i in $nativePkgs; do
+for i in "${!nativePkgs[@]}"; do
     _addToNativeEnv $i
 done
 
@@ -356,7 +353,7 @@ _addToCrossEnv() {
     runHook crossEnvHook "$pkg"
 }
 
-for i in $crossPkgs; do
+for i in "${!crossPkgs[@]}"; do
     _addToCrossEnv $i
 done