diff --git a/pkgs/development/interpreters/python/hooks/flit-build-hook.sh b/pkgs/development/interpreters/python/hooks/flit-build-hook.sh
index 23198bd711b86..45893aae00f4e 100644
--- a/pkgs/development/interpreters/python/hooks/flit-build-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/flit-build-hook.sh
@@ -9,7 +9,7 @@ flitBuildPhase () {
     echo "Finished executing flitBuildPhase"
 }
 
-if [ -z "${dontUseFlitBuild-}" ] && [ -z "$buildPhase" ]; then
+if [ -z "${dontUseFlitBuild-}" ] && [ -z "${buildPhase-}" ]; then
     echo "Using flitBuildPhase"
     buildPhase=flitBuildPhase
 fi
diff --git a/pkgs/development/interpreters/python/hooks/pip-build-hook.sh b/pkgs/development/interpreters/python/hooks/pip-build-hook.sh
index ac025165410ae..a58c01ce808cb 100644
--- a/pkgs/development/interpreters/python/hooks/pip-build-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/pip-build-hook.sh
@@ -31,7 +31,7 @@ pipShellHook() {
     echo "Finished executing pipShellHook"
 }
 
-if [ -z "${dontUsePipBuild-}" ] && [ -z "$buildPhase" ]; then
+if [ -z "${dontUsePipBuild-}" ] && [ -z "${buildPhase-}" ]; then
     echo "Using pipBuildPhase"
     buildPhase=pipBuildPhase
 fi
diff --git a/pkgs/development/interpreters/python/hooks/pip-install-hook.sh b/pkgs/development/interpreters/python/hooks/pip-install-hook.sh
index ca5aa2f983b24..4eefe22d3f288 100644
--- a/pkgs/development/interpreters/python/hooks/pip-install-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/pip-install-hook.sh
@@ -18,7 +18,7 @@ pipInstallPhase() {
     echo "Finished executing pipInstallPhase"
 }
 
-if [ -z "${dontUsePipInstall-}" ] && [ -z "$installPhase" ]; then
+if [ -z "${dontUsePipInstall-}" ] && [ -z "${installPhase-}" ]; then
     echo "Using pipInstallPhase"
     installPhase=pipInstallPhase
 fi
diff --git a/pkgs/development/interpreters/python/hooks/pytest-check-hook.sh b/pkgs/development/interpreters/python/hooks/pytest-check-hook.sh
index 9065b69fc09cd..18f05b6d218cd 100644
--- a/pkgs/development/interpreters/python/hooks/pytest-check-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/pytest-check-hook.sh
@@ -43,7 +43,7 @@ function pytestCheckPhase() {
     echo "Finished executing pytestCheckPhase"
 }
 
-if [ -z "${dontUsePytestCheck-}" ] && [ -z "$installCheckPhase" ]; then
+if [ -z "${dontUsePytestCheck-}" ] && [ -z "${installCheckPhase-}" ]; then
     echo "Using pytestCheckPhase"
     preDistPhases+=" pytestCheckPhase"
 fi
diff --git a/pkgs/development/interpreters/python/hooks/setuptools-build-hook.sh b/pkgs/development/interpreters/python/hooks/setuptools-build-hook.sh
index 648f19efb3631..ebda9e8b52309 100644
--- a/pkgs/development/interpreters/python/hooks/setuptools-build-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/setuptools-build-hook.sh
@@ -36,12 +36,12 @@ setuptoolsShellHook() {
     echo "Finished executing setuptoolsShellHook"
 }
 
-if [ -z "${dontUseSetuptoolsBuild-}" ] && [ -z "$buildPhase" ]; then
+if [ -z "${dontUseSetuptoolsBuild-}" ] && [ -z "${buildPhase-}" ]; then
     echo "Using setuptoolsBuildPhase"
     buildPhase=setuptoolsBuildPhase
 fi
 
-if [ -z "${dontUseSetuptoolsShellHook-}" ] && [ -z "$shellHook" ]; then
+if [ -z "${dontUseSetuptoolsShellHook-}" ] && [ -z "${shellHook-}" ]; then
     echo "Using setuptoolsShellHook"
     shellHook=setuptoolsShellHook
 fi
diff --git a/pkgs/development/interpreters/python/hooks/setuptools-check-hook.sh b/pkgs/development/interpreters/python/hooks/setuptools-check-hook.sh
index 5b07155ff4d6d..88b7b11931b02 100644
--- a/pkgs/development/interpreters/python/hooks/setuptools-check-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/setuptools-check-hook.sh
@@ -12,7 +12,7 @@ setuptoolsCheckPhase() {
     echo "Finished executing setuptoolsCheckPhase"
 }
 
-if [ -z "${dontUseSetuptoolsCheck-}" ] && [ -z "$installCheckPhase" ]; then
+if [ -z "${dontUseSetuptoolsCheck-}" ] && [ -z "${installCheckPhase-}" ]; then
     echo "Using setuptoolsCheckPhase"
     preDistPhases+=" setuptoolsCheckPhase"
 fi
diff --git a/pkgs/development/interpreters/python/hooks/wheel-unpack-hook.sh b/pkgs/development/interpreters/python/hooks/wheel-unpack-hook.sh
index 81efdb0d41102..fca808a933bad 100644
--- a/pkgs/development/interpreters/python/hooks/wheel-unpack-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/wheel-unpack-hook.sh
@@ -12,7 +12,7 @@ wheelUnpackPhase(){
     echo "Finished executing wheelUnpackPhase"
 }
 
-if [ -z "${dontUseWheelUnpack-}" ] && [ -z "$unpackPhase" ]; then
+if [ -z "${dontUseWheelUnpack-}" ] && [ -z "${unpackPhase-}" ]; then
     echo "Using wheelUnpackPhase"
     unpackPhase=wheelUnpackPhase
 fi
diff --git a/pkgs/development/libraries/gtk/hooks/drop-icon-theme-cache.sh b/pkgs/development/libraries/gtk/hooks/drop-icon-theme-cache.sh
index 8f2cb8a334aee..f28a856c4f50f 100644
--- a/pkgs/development/libraries/gtk/hooks/drop-icon-theme-cache.sh
+++ b/pkgs/development/libraries/gtk/hooks/drop-icon-theme-cache.sh
@@ -16,4 +16,4 @@ dropIconThemeCache() {
     fi
 }
 
-preFixupPhases="$preFixupPhases dropIconThemeCache"
+preFixupPhases="${preFixupPhases-} dropIconThemeCache"
diff --git a/pkgs/development/libraries/qt-5/hooks/qmake-hook.sh b/pkgs/development/libraries/qt-5/hooks/qmake-hook.sh
index fc4a0be628267..b785a779c8bc4 100644
--- a/pkgs/development/libraries/qt-5/hooks/qmake-hook.sh
+++ b/pkgs/development/libraries/qt-5/hooks/qmake-hook.sh
@@ -31,6 +31,6 @@ qmakeConfigurePhase() {
     runHook postConfigure
 }
 
-if [ -z "${dontUseQmakeConfigure-}" -a -z "$configurePhase" ]; then
+if [ -z "${dontUseQmakeConfigure-}" -a -z "${configurePhase-}" ]; then
     configurePhase=qmakeConfigurePhase
 fi
diff --git a/pkgs/development/tools/build-managers/cmake/setup-hook.sh b/pkgs/development/tools/build-managers/cmake/setup-hook.sh
index dbd40bf71242c..8bd54d3bc13d1 100755
--- a/pkgs/development/tools/build-managers/cmake/setup-hook.sh
+++ b/pkgs/development/tools/build-managers/cmake/setup-hook.sh
@@ -99,7 +99,7 @@ cmakeConfigurePhase() {
     cmakeFlags="-DCMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY=ON $cmakeFlags"
     cmakeFlags="-DCMAKE_FIND_PACKAGE_NO_SYSTEM_PACKAGE_REGISTRY=ON $cmakeFlags"
 
-    if [ "$buildPhase" = ninjaBuildPhase ]; then
+    if [ "${buildPhase-}" = ninjaBuildPhase ]; then
         cmakeFlags="-GNinja $cmakeFlags"
     fi
 
@@ -115,7 +115,7 @@ cmakeConfigurePhase() {
     runHook postConfigure
 }
 
-if [ -z "${dontUseCmakeConfigure-}" -a -z "$configurePhase" ]; then
+if [ -z "${dontUseCmakeConfigure-}" -a -z "${configurePhase-}" ]; then
     setOutputFlags=
     configurePhase=cmakeConfigurePhase
 fi
diff --git a/pkgs/development/tools/build-managers/gn/setup-hook.sh b/pkgs/development/tools/build-managers/gn/setup-hook.sh
index 4f772d2369bae..850f18948cad9 100644
--- a/pkgs/development/tools/build-managers/gn/setup-hook.sh
+++ b/pkgs/development/tools/build-managers/gn/setup-hook.sh
@@ -9,6 +9,6 @@ gnConfigurePhase() {
     runHook postConfigure
 }
 
-if [ -z "${dontUseGnConfigure-}" -a -z "$configurePhase" ]; then
+if [ -z "${dontUseGnConfigure-}" -a -z "${configurePhase-}" ]; then
     configurePhase=gnConfigurePhase
 fi
diff --git a/pkgs/development/tools/build-managers/meson/setup-hook.sh b/pkgs/development/tools/build-managers/meson/setup-hook.sh
index bfb40303cd85d..8d76ecdaf32ba 100644
--- a/pkgs/development/tools/build-managers/meson/setup-hook.sh
+++ b/pkgs/development/tools/build-managers/meson/setup-hook.sh
@@ -36,7 +36,7 @@ mesonConfigurePhase() {
     runHook postConfigure
 }
 
-if [ -z "${dontUseMesonConfigure-}" -a -z "$configurePhase" ]; then
+if [ -z "${dontUseMesonConfigure-}" -a -z "${configurePhase-}" ]; then
     setOutputFlags=
     configurePhase=mesonConfigurePhase
 fi
diff --git a/pkgs/development/tools/build-managers/ninja/setup-hook.sh b/pkgs/development/tools/build-managers/ninja/setup-hook.sh
index e4651db38a3b0..7d8087ad13422 100644
--- a/pkgs/development/tools/build-managers/ninja/setup-hook.sh
+++ b/pkgs/development/tools/build-managers/ninja/setup-hook.sh
@@ -19,7 +19,7 @@ ninjaBuildPhase() {
     runHook postBuild
 }
 
-if [ -z "$[dontUseNinjaBuild-}" -a -z "$buildPhase" ]; then
+if [ -z "${dontUseNinjaBuild-}" -a -z "${buildPhase-}" ]; then
     buildPhase=ninjaBuildPhase
 fi
 
@@ -38,7 +38,7 @@ ninjaInstallPhase() {
     runHook postInstall
 }
 
-if [ -z "${dontUseNinjaInstall-}" -a -z "$installPhase" ]; then
+if [ -z "${dontUseNinjaInstall-}" -a -z "${installPhase-}" ]; then
     installPhase=ninjaInstallPhase
 fi
 
@@ -73,6 +73,6 @@ ninjaCheckPhase() {
     runHook postCheck
 }
 
-if [ -z "${dontUseNinjaCheck-}" -a -z "$checkPhase" ]; then
+if [ -z "${dontUseNinjaCheck-}" -a -z "${checkPhase-}" ]; then
     checkPhase=ninjaCheckPhase
 fi
diff --git a/pkgs/development/tools/build-managers/scons/setup-hook.sh b/pkgs/development/tools/build-managers/scons/setup-hook.sh
index 428852ac574aa..0b908f68286b5 100644
--- a/pkgs/development/tools/build-managers/scons/setup-hook.sh
+++ b/pkgs/development/tools/build-managers/scons/setup-hook.sh
@@ -71,14 +71,14 @@ sconsCheckPhase() {
     runHook postCheck
 }
 
-if [ -z "$buildPhase" ]; then
+if [ -z "${buildPhase-}" ]; then
     buildPhase=sconsBuildPhase
 fi
 
-if [ -z "${dontUseSconsInstall-}" -a -z "$installPhase" ]; then
+if [ -z "${dontUseSconsInstall-}" -a -z "${installPhase-}" ]; then
     installPhase=sconsInstallPhase
 fi
 
-if [ -z "$checkPhase" ]; then
+if [ -z "${checkPhase-}" ]; then
     checkPhase=sconsCheckPhase
 fi
diff --git a/pkgs/development/tools/misc/premake/setup-hook.sh b/pkgs/development/tools/misc/premake/setup-hook.sh
index ba06ea2c76179..6e65e9e8c73f1 100644
--- a/pkgs/development/tools/misc/premake/setup-hook.sh
+++ b/pkgs/development/tools/misc/premake/setup-hook.sh
@@ -14,6 +14,6 @@ premakeConfigurePhase() {
     runHook postConfigure
 }
 
-if [ -z "$configurePhase" ]; then
+if [ -z "${configurePhase-}" ]; then
     configurePhase=premakeConfigurePhase
 fi
diff --git a/pkgs/development/tools/xcbuild/setup-hook.sh b/pkgs/development/tools/xcbuild/setup-hook.sh
index 9dc03a61f62ee..f4b5abf2d8d38 100644
--- a/pkgs/development/tools/xcbuild/setup-hook.sh
+++ b/pkgs/development/tools/xcbuild/setup-hook.sh
@@ -20,7 +20,7 @@ xcbuildInstallPhase () {
 }
 
 buildPhase=xcbuildBuildPhase
-if [ -z "$installPhase" ]; then
+if [ -z "${installPhase-}" ]; then
     installPhase=xcbuildInstallPhase
 fi
 
diff --git a/pkgs/servers/x11/xorg/imake-setup-hook.sh b/pkgs/servers/x11/xorg/imake-setup-hook.sh
index e743093af0ec5..351ffab34d0f0 100644
--- a/pkgs/servers/x11/xorg/imake-setup-hook.sh
+++ b/pkgs/servers/x11/xorg/imake-setup-hook.sh
@@ -14,6 +14,6 @@ imakeConfigurePhase() {
     runHook postConfigure
 }
 
-if [ -z "${dontUseImakeConfigure-}" -a -z "$configurePhase" ]; then
+if [ -z "${dontUseImakeConfigure-}" -a -z "${configurePhase-}" ]; then
     configurePhase=imakeConfigurePhase
 fi
diff --git a/pkgs/tools/misc/desktop-file-utils/setup-hook.sh b/pkgs/tools/misc/desktop-file-utils/setup-hook.sh
index 004d635cff0e5..728070e345810 100644
--- a/pkgs/tools/misc/desktop-file-utils/setup-hook.sh
+++ b/pkgs/tools/misc/desktop-file-utils/setup-hook.sh
@@ -3,4 +3,4 @@ mimeinfoPreFixupPhase() {
     rm -f $out/share/applications/mimeinfo.cache
 }
 
-preFixupPhases="$preFixupPhases mimeinfoPreFixupPhase"
+preFixupPhases="${preFixupPhases-} mimeinfoPreFixupPhase"