diff --git a/doc/stdenv/stdenv.chapter.md b/doc/stdenv/stdenv.chapter.md
index f776ca8d8dab..f4b659bb00a9 100644
--- a/doc/stdenv/stdenv.chapter.md
+++ b/doc/stdenv/stdenv.chapter.md
@@ -518,8 +518,10 @@ There are a number of variables that control what phases are executed and in wha
 
 Specifies the phases. You can change the order in which phases are executed, or add new phases, by setting this variable. If it’s not set, the default value is used, which is `$prePhases unpackPhase patchPhase $preConfigurePhases configurePhase $preBuildPhases buildPhase checkPhase $preInstallPhases installPhase fixupPhase installCheckPhase $preDistPhases distPhase $postPhases`.
 
+The elements of `phases` must not contain spaces. If `phases` is specified as a Nix Language attribute, it should be specified as lists instead of strings. The same rules apply to the `*Phases` variables.
+
 It is discouraged to set this variable, as it is easy to miss some important functionality hidden in some of the less obviously needed phases (like `fixupPhase` which patches the shebang of scripts).
-Usually, if you just want to add a few phases, it’s more convenient to set one of the variables below (such as `preInstallPhases`).
+Usually, if you just want to add a few phases, it’s more convenient to set one of the `*Phases` variables below.
 
 ##### `prePhases` {#var-stdenv-prePhases}
 
diff --git a/pkgs/applications/editors/vim/plugins/neovim-require-check-hook.sh b/pkgs/applications/editors/vim/plugins/neovim-require-check-hook.sh
index 0c6a0010845d..e901e4fd2774 100644
--- a/pkgs/applications/editors/vim/plugins/neovim-require-check-hook.sh
+++ b/pkgs/applications/editors/vim/plugins/neovim-require-check-hook.sh
@@ -16,6 +16,6 @@ neovimRequireCheckHook () {
 }
 
 echo "Using neovimRequireCheckHook"
-preDistPhases+=" neovimRequireCheckHook"
+appendToVar preDistPhases neovimRequireCheckHook
 
 
diff --git a/pkgs/applications/editors/vim/plugins/vim-command-check-hook.sh b/pkgs/applications/editors/vim/plugins/vim-command-check-hook.sh
index c4ddd8e0c5af..402910fd0cbd 100644
--- a/pkgs/applications/editors/vim/plugins/vim-command-check-hook.sh
+++ b/pkgs/applications/editors/vim/plugins/vim-command-check-hook.sh
@@ -21,5 +21,5 @@ vimCommandCheckHook () {
 }
 
 echo "Using vimCommandCheckHook"
-preDistPhases+=" vimCommandCheckHook"
+appendToVar preDistPhases vimCommandCheckHook
 
diff --git a/pkgs/applications/graphics/gimp/plugins/default.nix b/pkgs/applications/graphics/gimp/plugins/default.nix
index 667a1d505751..5280a1ae719e 100644
--- a/pkgs/applications/graphics/gimp/plugins/default.nix
+++ b/pkgs/applications/graphics/gimp/plugins/default.nix
@@ -17,7 +17,7 @@ let
   pluginDerivation = attrs: let
     name = attrs.name or "${attrs.pname}-${attrs.version}";
   in stdenv.mkDerivation ({
-    prePhases = "extraLib";
+    prePhases = [ "extraLib" ];
     extraLib = ''
       installScripts(){
         mkdir -p $out/${gimp.targetScriptDir}/${name};
@@ -54,7 +54,7 @@ let
   });
 
   scriptDerivation = {src, ...}@attrs : pluginDerivation ({
-    prePhases = "extraLib";
+    prePhases = [ "extraLib" ];
     dontUnpack = true;
     installPhase = ''
       runHook preInstall
diff --git a/pkgs/build-support/coq/default.nix b/pkgs/build-support/coq/default.nix
index e55e22215daa..cafd2421f21d 100644
--- a/pkgs/build-support/coq/default.nix
+++ b/pkgs/build-support/coq/default.nix
@@ -146,7 +146,7 @@ stdenv.mkDerivation (removeAttrs ({
 })
 // (optionalAttrs (args?useMelquiondRemake) rec {
   COQUSERCONTRIB = "$out/lib/coq/${coq.coq-version}/user-contrib";
-  preConfigurePhases = "autoconf";
+  preConfigurePhases = [ "autoconf" ];
   configureFlags = [ "--libdir=${COQUSERCONTRIB}/${useMelquiondRemake.logpath or ""}" ];
   buildPhase = "./remake -j$NIX_BUILD_CORES";
   installPhase = "./remake install";
diff --git a/pkgs/build-support/make-darwin-bundle/default.nix b/pkgs/build-support/make-darwin-bundle/default.nix
index 52dd54b0b2c4..a80ebf8fac9e 100644
--- a/pkgs/build-support/make-darwin-bundle/default.nix
+++ b/pkgs/build-support/make-darwin-bundle/default.nix
@@ -22,5 +22,5 @@ writeShellScript "make-darwin-bundle-${name}" (''
     ${writeDarwinBundle}/bin/write-darwin-bundle "''${!outputBin}" "${name}" "${exec}"
   }
 
-  preDistPhases+=" makeDarwinBundlePhase"
+  appendToVar preDistPhases makeDarwinBundlePhase
 '')
diff --git a/pkgs/build-support/release/binary-tarball.nix b/pkgs/build-support/release/binary-tarball.nix
index 37c5f8c7ee86..aeaa8edb52be 100644
--- a/pkgs/build-support/release/binary-tarball.nix
+++ b/pkgs/build-support/release/binary-tarball.nix
@@ -24,7 +24,7 @@ stdenv.mkDerivation (
 
     prefix = "/usr/local";
 
-    postPhases = "finalPhase";
+    postPhases = [ "finalPhase" ];
   }
 
   // args //
diff --git a/pkgs/build-support/release/debian-build.nix b/pkgs/build-support/release/debian-build.nix
index ab84a504b54c..e73b39c4e6b6 100644
--- a/pkgs/build-support/release/debian-build.nix
+++ b/pkgs/build-support/release/debian-build.nix
@@ -18,7 +18,7 @@ vmTools.runInLinuxImage (stdenv.mkDerivation (
 
     prefix = "/usr";
 
-    prePhases = "installExtraDebsPhase sysInfoPhase";
+    prePhases = [ "installExtraDebsPhase" "sysInfoPhase" ];
   }
 
   // removeAttrs args ["vmTools" "lib"] //
diff --git a/pkgs/build-support/release/source-tarball.nix b/pkgs/build-support/release/source-tarball.nix
index fbc8bc6b258b..4effd63f740b 100644
--- a/pkgs/build-support/release/source-tarball.nix
+++ b/pkgs/build-support/release/source-tarball.nix
@@ -31,8 +31,8 @@ stdenv.mkDerivation (
 
     showBuildStats = true;
 
-    preConfigurePhases = "autoconfPhase";
-    postPhases = "finalPhase";
+    preConfigurePhases = [ "autoconfPhase" ];
+    postPhases = [ "finalPhase" ];
 
     # Autoconfiscate the sources.
     autoconfPhase = ''
diff --git a/pkgs/build-support/setup-hooks/autoreconf.sh b/pkgs/build-support/setup-hooks/autoreconf.sh
index bb168aad4c51..3d12a17b78c1 100644
--- a/pkgs/build-support/setup-hooks/autoreconf.sh
+++ b/pkgs/build-support/setup-hooks/autoreconf.sh
@@ -1,4 +1,4 @@
-preConfigurePhases="${preConfigurePhases:-} autoreconfPhase"
+appendToVar preConfigurePhases autoreconfPhase
 
 autoreconfPhase() {
     runHook preAutoreconf
diff --git a/pkgs/build-support/setup-hooks/enable-coverage-instrumentation.sh b/pkgs/build-support/setup-hooks/enable-coverage-instrumentation.sh
index 2b48fea4ff0b..61e9ed5705f4 100644
--- a/pkgs/build-support/setup-hooks/enable-coverage-instrumentation.sh
+++ b/pkgs/build-support/setup-hooks/enable-coverage-instrumentation.sh
@@ -1,4 +1,4 @@
-postPhases+=" cleanupBuildDir"
+appendToVar postPhases cleanupBuildDir
 
 # Force GCC to build with coverage instrumentation.  Also disable
 # optimisation, since it may confuse things.
diff --git a/pkgs/build-support/setup-hooks/keep-build-tree.sh b/pkgs/build-support/setup-hooks/keep-build-tree.sh
index 754900bfc337..653149bdf26f 100644
--- a/pkgs/build-support/setup-hooks/keep-build-tree.sh
+++ b/pkgs/build-support/setup-hooks/keep-build-tree.sh
@@ -1,4 +1,4 @@
-prePhases+=" moveBuildDir"
+appendToVar prePhases moveBuildDir
 
 moveBuildDir() {
     mkdir -p $out/.build
diff --git a/pkgs/build-support/setup-hooks/make-coverage-analysis-report.sh b/pkgs/build-support/setup-hooks/make-coverage-analysis-report.sh
index 9108b4c50355..d6a03019dc51 100644
--- a/pkgs/build-support/setup-hooks/make-coverage-analysis-report.sh
+++ b/pkgs/build-support/setup-hooks/make-coverage-analysis-report.sh
@@ -1,4 +1,4 @@
-postPhases+=" coverageReportPhase"
+appendToVar postPhases coverageReportPhase
 
 coverageReportPhase() {
     lcov --directory . --capture --output-file app.info
diff --git a/pkgs/build-support/setup-hooks/move-build-tree.sh b/pkgs/build-support/setup-hooks/move-build-tree.sh
index 2718070f3933..29495e1d9f29 100644
--- a/pkgs/build-support/setup-hooks/move-build-tree.sh
+++ b/pkgs/build-support/setup-hooks/move-build-tree.sh
@@ -1,11 +1,11 @@
-prePhases+=" moveBuildDir"
+appendToVar prePhases moveBuildDir
 
 moveBuildDir() {
     mkdir -p $out/.build
     cd $out/.build
 }
 
-postPhases+=" removeBuildDir"
+appendToVar postPhases removeBuildDir
 
 removeBuildDir() {
     rm -rf $out/.build
diff --git a/pkgs/build-support/setup-hooks/update-autotools-gnu-config-scripts.sh b/pkgs/build-support/setup-hooks/update-autotools-gnu-config-scripts.sh
index ebd3afa05d94..0c5e1a81c7af 100644
--- a/pkgs/build-support/setup-hooks/update-autotools-gnu-config-scripts.sh
+++ b/pkgs/build-support/setup-hooks/update-autotools-gnu-config-scripts.sh
@@ -1,4 +1,4 @@
-preConfigurePhases+=" updateAutotoolsGnuConfigScriptsPhase"
+appendToVar preConfigurePhases updateAutotoolsGnuConfigScriptsPhase
 
 updateAutotoolsGnuConfigScriptsPhase() {
     if [ -n "${dontUpdateAutotoolsGnuConfigScripts-}" ]; then return; fi
diff --git a/pkgs/by-name/ha/hare/setup-hook.sh b/pkgs/by-name/ha/hare/setup-hook.sh
index 3a427fd70328..388ed9bcf25f 100644
--- a/pkgs/by-name/ha/hare/setup-hook.sh
+++ b/pkgs/by-name/ha/hare/setup-hook.sh
@@ -18,7 +18,7 @@ echoCmd "HAREPATH" "$HAREPATH"
 echoCmd "hare" "$(command -v hare)"
 echoCmd "hare-native" "$(command -v hare-native)"
 '
-prePhases+=("hareSetStdlibPhase" "hareInfoPhase")
+appendToVar prePhases hareSetStdlibPhase hareInfoPhase
 
 readonly hare_unconditional_flags="@hare_unconditional_flags@"
 case "${hareBuildType:-"release"}" in
diff --git a/pkgs/desktops/gnustep/make/setup-hook.sh b/pkgs/desktops/gnustep/make/setup-hook.sh
index 0bfbd35f45f5..202084cc671d 100644
--- a/pkgs/desktops/gnustep/make/setup-hook.sh
+++ b/pkgs/desktops/gnustep/make/setup-hook.sh
@@ -18,7 +18,7 @@ addGnustepInstallFlags() {
     )
 }
 
-preInstallPhases+=" addGnustepInstallFlags"
+appendToVar preInstallPhases addGnustepInstallFlags
 
 addGNUstepEnvVars() {
     local filename
diff --git a/pkgs/desktops/xfce/core/xfce4-dev-tools/setup-hook.sh b/pkgs/desktops/xfce/core/xfce4-dev-tools/setup-hook.sh
index 05ddc6a172ff..57a7a6c8995a 100644
--- a/pkgs/desktops/xfce/core/xfce4-dev-tools/setup-hook.sh
+++ b/pkgs/desktops/xfce/core/xfce4-dev-tools/setup-hook.sh
@@ -10,5 +10,5 @@ xdtAutogenPhase() {
 }
 
 if [ -z "${dontUseXdtAutogenPhase-}" ]; then
-    preConfigurePhases+=(xdtAutogenPhase)
+    appendToVar preConfigurePhases xdtAutogenPhase
 fi
diff --git a/pkgs/development/compilers/dotnet/dotnet-sdk-setup-hook.sh b/pkgs/development/compilers/dotnet/dotnet-sdk-setup-hook.sh
index fccf6b02aaeb..530e99755d65 100644
--- a/pkgs/development/compilers/dotnet/dotnet-sdk-setup-hook.sh
+++ b/pkgs/development/compilers/dotnet/dotnet-sdk-setup-hook.sh
@@ -77,6 +77,6 @@ configureNuget() {
 }
 
 if [[ -z ${dontConfigureNuget-} ]]; then
-    prePhases+=(createNugetDirs)
-    preConfigurePhases+=(configureNuget)
+    appendToVar prePhases createNugetDirs
+    appendToVar preConfigurePhases configureNuget
 fi
diff --git a/pkgs/development/interpreters/octave/hooks/octave-write-required-octave-packages-hook.sh b/pkgs/development/interpreters/octave/hooks/octave-write-required-octave-packages-hook.sh
index 64e87d68246f..fb808485a36a 100644
--- a/pkgs/development/interpreters/octave/hooks/octave-write-required-octave-packages-hook.sh
+++ b/pkgs/development/interpreters/octave/hooks/octave-write-required-octave-packages-hook.sh
@@ -13,5 +13,5 @@ octaveWriteRequiredOctavePackagesPhase() {
 # Yes its a bit long...
 if [ -z "${dontWriteRequiredOctavePackagesPhase-}" ]; then
     echo "Using octaveWriteRequiredOctavePackagesPhase"
-    preDistPhases+=" octaveWriteRequiredOctavePackagesPhase"
+    appendToVar preDistPhases octaveWriteRequiredOctavePackagesPhase
 fi
diff --git a/pkgs/development/interpreters/octave/hooks/write-required-octave-packages-hook.sh b/pkgs/development/interpreters/octave/hooks/write-required-octave-packages-hook.sh
index 032ea398ac56..6c5de6e4fc4f 100644
--- a/pkgs/development/interpreters/octave/hooks/write-required-octave-packages-hook.sh
+++ b/pkgs/development/interpreters/octave/hooks/write-required-octave-packages-hook.sh
@@ -13,5 +13,5 @@ writeRequiredOctavePackagesPhase() {
 # Yes its a bit long...
 if [ -z "${dontWriteRequiredOctavePackagesPhase-}" ]; then
     echo "Using writeRequiredOctavePackagesPhase"
-    preDistPhases+=" writeRequiredOctavePackagesPhase"
+    appendToVar preDistPhases writeRequiredOctavePackagesPhase
 fi
diff --git a/pkgs/development/interpreters/python/hooks/pytest-check-hook.sh b/pkgs/development/interpreters/python/hooks/pytest-check-hook.sh
index 06694e79e492..a9e82674c5f8 100644
--- a/pkgs/development/interpreters/python/hooks/pytest-check-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/pytest-check-hook.sh
@@ -58,5 +58,5 @@ function pytestCheckPhase() {
 
 if [ -z "${dontUsePytestCheck-}" ] && [ -z "${installCheckPhase-}" ]; then
     echo "Using pytestCheckPhase"
-    preDistPhases+=" pytestCheckPhase"
+    appendToVar preDistPhases pytestCheckPhase
 fi
diff --git a/pkgs/development/interpreters/python/hooks/python-catch-conflicts-hook.sh b/pkgs/development/interpreters/python/hooks/python-catch-conflicts-hook.sh
index 0abcad3c42f2..6ba3d7f65cb4 100644
--- a/pkgs/development/interpreters/python/hooks/python-catch-conflicts-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/python-catch-conflicts-hook.sh
@@ -6,5 +6,5 @@ pythonCatchConflictsPhase() {
 }
 
 if [ -z "${dontUsePythonCatchConflicts-}" ]; then
-    preDistPhases+=" pythonCatchConflictsPhase"
+    appendToVar preDistPhases pythonCatchConflictsPhase
 fi
diff --git a/pkgs/development/interpreters/python/hooks/python-imports-check-hook.sh b/pkgs/development/interpreters/python/hooks/python-imports-check-hook.sh
index b65d6e745247..f4ef271ac1b2 100644
--- a/pkgs/development/interpreters/python/hooks/python-imports-check-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/python-imports-check-hook.sh
@@ -18,5 +18,5 @@ pythonImportsCheckPhase () {
 
 if [ -z "${dontUsePythonImportsCheck-}" ]; then
     echo "Using pythonImportsCheckPhase"
-    preDistPhases+=" pythonImportsCheckPhase"
+    appendToVar preDistPhases pythonImportsCheckPhase
 fi
diff --git a/pkgs/development/interpreters/python/hooks/python-recompile-bytecode-hook.sh b/pkgs/development/interpreters/python/hooks/python-recompile-bytecode-hook.sh
index 649d0c17ea0c..7ac8c2d5cc72 100644
--- a/pkgs/development/interpreters/python/hooks/python-recompile-bytecode-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/python-recompile-bytecode-hook.sh
@@ -20,5 +20,5 @@ pythonRecompileBytecodePhase () {
 }
 
 if [ -z "${dontUsePythonRecompileBytecode-}" ]; then
-    postPhases+=" pythonRecompileBytecodePhase"
+    appendToVar postPhases pythonRecompileBytecodePhase
 fi
diff --git a/pkgs/development/interpreters/python/hooks/python-remove-bin-bytecode-hook.sh b/pkgs/development/interpreters/python/hooks/python-remove-bin-bytecode-hook.sh
index 1180694294db..d67c0c557353 100644
--- a/pkgs/development/interpreters/python/hooks/python-remove-bin-bytecode-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/python-remove-bin-bytecode-hook.sh
@@ -13,5 +13,5 @@ pythonRemoveBinBytecodePhase () {
 }
 
 if [ -z "${dontUsePythonRemoveBinBytecode-}" ]; then
-    preDistPhases+=" pythonRemoveBinBytecodePhase"
+    appendToVar preDistPhases pythonRemoveBinBytecodePhase
 fi
diff --git a/pkgs/development/interpreters/python/hooks/python-runtime-deps-check-hook.sh b/pkgs/development/interpreters/python/hooks/python-runtime-deps-check-hook.sh
index 43a2f9b88745..dc888262ea0d 100644
--- a/pkgs/development/interpreters/python/hooks/python-runtime-deps-check-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/python-runtime-deps-check-hook.sh
@@ -16,5 +16,5 @@ pythonRuntimeDepsCheckHook() {
 
 if [ -z "${dontCheckRuntimeDeps-}" ]; then
     echo "Using pythonRuntimeDepsCheckHook"
-    preInstallPhases+=" pythonRuntimeDepsCheckHook"
+    appendToVar preInstallPhases pythonRuntimeDepsCheckHook
 fi
diff --git a/pkgs/development/interpreters/python/hooks/sphinx-hook.sh b/pkgs/development/interpreters/python/hooks/sphinx-hook.sh
index 0307e83d9479..0f32a6ec0e82 100644
--- a/pkgs/development/interpreters/python/hooks/sphinx-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/sphinx-hook.sh
@@ -69,4 +69,4 @@ installSphinxPhase() {
     runHook postInstallSphinx
 }
 
-preDistPhases+=" buildSphinxPhase installSphinxPhase"
+appendToVar preDistPhases buildSphinxPhase installSphinxPhase
diff --git a/pkgs/development/interpreters/python/hooks/unittest-check-hook.sh b/pkgs/development/interpreters/python/hooks/unittest-check-hook.sh
index f4bd34747730..64ecb13cbc71 100644
--- a/pkgs/development/interpreters/python/hooks/unittest-check-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/unittest-check-hook.sh
@@ -13,5 +13,5 @@ unittestCheckPhase() {
 
 if [ -z "${dontUseUnittestCheck-}" ] && [ -z "${installCheckPhase-}" ]; then
     echo "Using unittestCheckPhase"
-    preDistPhases+=" unittestCheckPhase"
+    appendToVar preDistPhases unittestCheckPhase
 fi
diff --git a/pkgs/development/libraries/glib/setup-hook.sh b/pkgs/development/libraries/glib/setup-hook.sh
index 8ead5510ec4f..9eabf8a679a9 100644
--- a/pkgs/development/libraries/glib/setup-hook.sh
+++ b/pkgs/development/libraries/glib/setup-hook.sh
@@ -12,7 +12,7 @@ addEnvHooks "$targetOffset" make_glib_find_gsettings_schemas
 glibPreInstallPhase() {
   makeFlagsArray+=("gsettingsschemadir=${!outputLib}/share/gsettings-schemas/$name/glib-2.0/schemas/")
 }
-preInstallPhases+=" glibPreInstallPhase"
+appendToVar preInstallPhases glibPreInstallPhase
 
 glibPreFixupPhase() {
     # Move gschemas in case the install flag didn't help
diff --git a/pkgs/development/libraries/liquidfun/default.nix b/pkgs/development/libraries/liquidfun/default.nix
index 6ab138016d19..2e12f5903444 100644
--- a/pkgs/development/libraries/liquidfun/default.nix
+++ b/pkgs/development/libraries/liquidfun/default.nix
@@ -15,7 +15,7 @@ stdenv.mkDerivation rec {
 
   sourceRoot = "liquidfun/Box2D";
 
-  preConfigurePhases = "preConfigure";
+  preConfigurePhases = [ "preConfigure" ];
 
   preConfigure = ''
     sed -i Box2D/Common/b2Settings.h -e 's@b2_maxPolygonVertices .*@b2_maxPolygonVertices 15@'
diff --git a/pkgs/development/libraries/qt-5/hooks/qmake-hook.sh b/pkgs/development/libraries/qt-5/hooks/qmake-hook.sh
index f52de4e51df2..855efb5e6c0f 100644
--- a/pkgs/development/libraries/qt-5/hooks/qmake-hook.sh
+++ b/pkgs/development/libraries/qt-5/hooks/qmake-hook.sh
@@ -20,7 +20,7 @@ qmakePrePhase() {
     # do the stripping ourselves (needed for separateDebugInfo)
     prependToVar qmakeFlags "CONFIG+=nostrip"
 }
-prePhases+=" qmakePrePhase"
+appendToVar prePhases qmakePrePhase
 
 qmakeConfigurePhase() {
     runHook preConfigure
diff --git a/pkgs/development/libraries/qt-5/hooks/qtbase-setup-hook.sh b/pkgs/development/libraries/qt-5/hooks/qtbase-setup-hook.sh
index 1b57d676e1fc..1b189d24d9ee 100644
--- a/pkgs/development/libraries/qt-5/hooks/qtbase-setup-hook.sh
+++ b/pkgs/development/libraries/qt-5/hooks/qtbase-setup-hook.sh
@@ -97,7 +97,7 @@ postPatchMkspecs() {
     fi
 }
 if [ -z "${dontPatchMkspecs-}" ]; then
-    postPhases="${postPhases-}${postPhases:+ }postPatchMkspecs"
+    appendToVar postPhases postPatchMkspecs
 fi
 
 qtPreHook() {
@@ -107,6 +107,6 @@ qtPreHook() {
         exit 1
     fi
 }
-prePhases+=" qtPreHook"
+appendToVar prePhases qtPreHook
 
 fi
diff --git a/pkgs/development/libraries/qt-6/hooks/qmake-hook.sh b/pkgs/development/libraries/qt-6/hooks/qmake-hook.sh
index 84b2fb153d9f..1f696be3e738 100644
--- a/pkgs/development/libraries/qt-6/hooks/qmake-hook.sh
+++ b/pkgs/development/libraries/qt-6/hooks/qmake-hook.sh
@@ -13,7 +13,7 @@ qmakePrePhase() {
       "NIX_OUTPUT_QML=${!outputBin}/${qtQmlPrefix:?}" \
       "NIX_OUTPUT_PLUGIN=${!outputBin}/${qtPluginPrefix:?}"
 }
-prePhases+=" qmakePrePhase"
+appendToVar prePhases qmakePrePhase
 
 qmakeConfigurePhase() {
     runHook preConfigure
diff --git a/pkgs/development/libraries/qt-6/hooks/qtbase-setup-hook.sh b/pkgs/development/libraries/qt-6/hooks/qtbase-setup-hook.sh
index 5006d6b65530..1ccfbd0cba38 100644
--- a/pkgs/development/libraries/qt-6/hooks/qtbase-setup-hook.sh
+++ b/pkgs/development/libraries/qt-6/hooks/qtbase-setup-hook.sh
@@ -71,7 +71,7 @@ else # Only set up Qt once.
         fi
     }
     if [ -z "${dontPatchMkspecs-}" ]; then
-        postPhases="${postPhases-}${postPhases:+ }postPatchMkspecs"
+        appendToVar postPhases postPatchMkspecs
     fi
 
     qtPreHook() {
@@ -81,7 +81,7 @@ else # Only set up Qt once.
             exit 1
         fi
     }
-    prePhases+=" qtPreHook"
+    appendToVar prePhases qtPreHook
 
     addQtModulePrefix() {
         addToSearchPath QT_ADDITIONAL_PACKAGES_PREFIX_PATH $1
diff --git a/pkgs/development/python-modules/pytest-forked/setup-hook.sh b/pkgs/development/python-modules/pytest-forked/setup-hook.sh
index e613feadf834..0eff690e9079 100644
--- a/pkgs/development/python-modules/pytest-forked/setup-hook.sh
+++ b/pkgs/development/python-modules/pytest-forked/setup-hook.sh
@@ -16,10 +16,17 @@ pytestForkedHook() {
 # until we have dependency mechanism in generic builder, we need to use this ugly hack.
 
 if [ -z "${dontUsePytestForked-}" ] && [ -z "${dontUsePytestCheck-}" ]; then
-    if [[ " ${preDistPhases:-} " =~ " pytestCheckPhase " ]]; then
-        preDistPhases+=" "
-        preDistPhases="${preDistPhases/ pytestCheckPhase / pytestForkedHook pytestCheckPhase }"
+    if [[ " ${preDistPhases[*]:-} " =~ " pytestCheckPhase " ]]; then
+        _preDistPhases="${preDistPhases[*]} "
+        _preDistPhases="${_preDistPhases/ pytestCheckPhase / pytestForkedHook pytestCheckPhase }"
+        if [[ -n "${__structuredAttrs-}" ]]; then
+            preDistPhases=()
+        else
+            preDistPhases=""
+        fi
+        appendToVar preDistPhases $_preDistPhases
+        unset _preDistPhases
     else
-        preDistPhases+=" pytestForkedHook"
+        appendToVar preDistPhases pytestForkedHook
     fi
 fi
diff --git a/pkgs/development/python-modules/pytest-xdist/setup-hook.sh b/pkgs/development/python-modules/pytest-xdist/setup-hook.sh
index 4c6473cea64d..9819e0d3ec7d 100644
--- a/pkgs/development/python-modules/pytest-xdist/setup-hook.sh
+++ b/pkgs/development/python-modules/pytest-xdist/setup-hook.sh
@@ -8,10 +8,17 @@ pytestXdistHook() {
 # until we have dependency mechanism in generic builder, we need to use this ugly hack.
 
 if [ -z "${dontUsePytestXdist-}" ] && [ -z "${dontUsePytestCheck-}" ]; then
-    if [[ " ${preDistPhases:-} " =~ " pytestCheckPhase " ]]; then
-        preDistPhases+=" "
-        preDistPhases="${preDistPhases/ pytestCheckPhase / pytestXdistHook pytestCheckPhase }"
+    if [[ " ${preDistPhases[*]:-} " =~ " pytestCheckPhase " ]]; then
+        _preDistPhases="${preDistPhases[*]} "
+        _preDistPhases="${_preDistPhases/ pytestCheckPhase / pytestXdistHook pytestCheckPhase }"
+        if [[ -n "${__structuredAttrs-}" ]]; then
+            preDistPhases=()
+        else
+            preDistPhases=""
+        fi
+        appendToVar preDistPhases $_preDistPhases
+        unset _preDistPhases
     else
-        preDistPhases+=" pytestXdistHook"
+        appendToVar preDistPhases pytestXdistHook
     fi
 fi
diff --git a/pkgs/development/python-modules/pytest/7.nix b/pkgs/development/python-modules/pytest/7.nix
index 8ca33b158e5c..3468bc73c098 100644
--- a/pkgs/development/python-modules/pytest/7.nix
+++ b/pkgs/development/python-modules/pytest/7.nix
@@ -87,7 +87,7 @@ let
       pytestcachePhase() {
           find $out -name .pytest_cache -type d -exec rm -rf {} +
       }
-      preDistPhases+=" pytestcachePhase"
+      appendToVar preDistPhases pytestcachePhase
 
       # pytest generates it's own bytecode files to improve assertion messages.
       # These files similar to cpython's bytecode files but are never laoded
@@ -100,7 +100,7 @@ let
           #    https://github.com/pytest-dev/pytest/blob/7.2.1/src/_pytest/assertion/rewrite.py#L51-L53
           find $out -name "*-pytest-*.py[co]" -delete
       }
-      preDistPhases+=" pytestRemoveBytecodePhase"
+      appendToVar preDistPhases pytestRemoveBytecodePhase
     '';
 
     pythonImportsCheck = [ "pytest" ];
diff --git a/pkgs/development/python-modules/pytest/default.nix b/pkgs/development/python-modules/pytest/default.nix
index fc5ca9c2a37b..1dcc23658394 100644
--- a/pkgs/development/python-modules/pytest/default.nix
+++ b/pkgs/development/python-modules/pytest/default.nix
@@ -84,7 +84,7 @@ buildPythonPackage rec {
     pytestcachePhase() {
         find $out -name .pytest_cache -type d -exec rm -rf {} +
     }
-    preDistPhases+=" pytestcachePhase"
+    appendToVar preDistPhases pytestcachePhase
 
     # pytest generates it's own bytecode files to improve assertion messages.
     # These files similar to cpython's bytecode files but are never laoded
@@ -97,7 +97,7 @@ buildPythonPackage rec {
         #    https://github.com/pytest-dev/pytest/blob/7.2.1/src/_pytest/assertion/rewrite.py#L51-L53
         find $out -name "*-pytest-*.py[co]" -delete
     }
-    preDistPhases+=" pytestRemoveBytecodePhase"
+    appendToVar preDistPhases pytestRemoveBytecodePhase
   '';
 
   pythonImportsCheck = [ "pytest" ];
diff --git a/pkgs/development/python2-modules/pytest/default.nix b/pkgs/development/python2-modules/pytest/default.nix
index 0edfd3039112..fa086eb46c7c 100644
--- a/pkgs/development/python2-modules/pytest/default.nix
+++ b/pkgs/development/python2-modules/pytest/default.nix
@@ -42,7 +42,7 @@ buildPythonPackage rec {
         find $out -name .pytest_cache -type d -exec rm -rf {} +
     }
 
-    preDistPhases+=" pytestcachePhase"
+    appendToVar preDistPhases pytestcachePhase
 
     # pytest generates it's own bytecode files to improve assertion messages.
     # These files similar to cpython's bytecode files but are never laoded
@@ -55,7 +55,7 @@ buildPythonPackage rec {
         #    https://github.com/pytest-dev/pytest/blob/4.6.11/src/_pytest/assertion/rewrite.py#L32-L47
         find $out -name "*-PYTEST.py[co]" -delete
     }
-    preDistPhases+=" pytestRemoveBytecodePhase"
+    appendToVar preDistPhases pytestRemoveBytecodePhase
   '';
 
   meta = with lib; {
diff --git a/pkgs/servers/home-assistant/build-custom-component/manifest-requirements-check-hook.sh b/pkgs/servers/home-assistant/build-custom-component/manifest-requirements-check-hook.sh
index 74f29ca399ed..1fb366d13b43 100644
--- a/pkgs/servers/home-assistant/build-custom-component/manifest-requirements-check-hook.sh
+++ b/pkgs/servers/home-assistant/build-custom-component/manifest-requirements-check-hook.sh
@@ -21,5 +21,5 @@ function manifestCheckPhase() {
 
 if [ -z "${dontCheckManifest-}" ] && [ -z "${installCheckPhase-}" ]; then
     echo "Using manifestCheckPhase"
-    preDistPhases+=" manifestCheckPhase"
+    appendToVar preDistPhases manifestCheckPhase
 fi