diff --git a/pkgs/by-name/wa/waf/setup-hook.sh b/pkgs/by-name/wa/waf/setup-hook.sh
index a154ae378a07..692341fb5a04 100644
--- a/pkgs/by-name/wa/waf/setup-hook.sh
+++ b/pkgs/by-name/wa/waf/setup-hook.sh
@@ -16,11 +16,8 @@ wafConfigurePhase() {
       export PKGCONFIG="${PKG_CONFIG}"
     fi
 
-    local flagsArray=(
-        $prefixFlag
-        $wafConfigureFlags "${wafConfigureFlagsArray[@]}"
-        ${wafConfigureTargets:-configure}
-    )
+    local flagsArray=( $prefixFlag )
+    concatTo flagsArray wafConfigureFlags wafConfigureFlagsArray wafConfigureTargets=configure
 
     echoCmd 'waf configure flags' "${flagsArray[@]}"
     python "$wafPath" "${flagsArray[@]}"
@@ -41,15 +38,8 @@ wafConfigurePhase() {
 wafBuildPhase () {
     runHook preBuild
 
-    # set to empty if unset
-    : "${wafFlags=}"
-
-    local flagsArray=(
-      ${enableParallelBuilding:+-j ${NIX_BUILD_CORES}}
-      $wafFlags ${wafFlagsArray[@]}
-      $wafBuildFlags ${wafBuildFlagsArray[@]}
-      ${wafBuildTargets:-build}
-    )
+    local flagsArray=( ${enableParallelBuilding:+-j ${NIX_BUILD_CORES}} )
+    concatTo flagsArray wafFlags wafFlagsArray wafBuildFlags wafBuildFlagsArray wafBuildTargets=build
 
     echoCmd 'waf build flags' "${flagsArray[@]}"
     python "$wafPath" "${flagsArray[@]}"
@@ -64,12 +54,8 @@ wafInstallPhase() {
         mkdir -p "$prefix"
     fi
 
-    local flagsArray=(
-        ${enableParallelInstalling:+-j ${NIX_BUILD_CORES}}
-        $wafFlags ${wafFlagsArray[@]}
-        $wafInstallFlags ${wafInstallFlagsArray[@]}
-        ${wafInstallTargets:-install}
-    )
+    local flagsArray=( ${enableParallelInstalling:+-j ${NIX_BUILD_CORES}} )
+    concatTo flagsArray wafFlags wafFlagsArray wafInstallFlags wafInstallFlagsArray wafInstallTargets=install
 
     echoCmd 'waf install flags' "${flagsArray[@]}"
     python "$wafPath" "${flagsArray[@]}"