diff --git a/pkgs/development/libraries/qt-6/hooks/wrap-qt-apps-hook.sh b/pkgs/development/libraries/qt-6/hooks/wrap-qt-apps-hook.sh
index 2d858055693c..39b8635e264d 100644
--- a/pkgs/development/libraries/qt-6/hooks/wrap-qt-apps-hook.sh
+++ b/pkgs/development/libraries/qt-6/hooks/wrap-qt-apps-hook.sh
@@ -63,7 +63,7 @@ if [[ -z "${__nix_wrapQtAppsHook-}" ]]; then
         qtHostPathHook "${!outputBin}"
     }
 
-    preFixupPhases+=" qtOwnPathsHook"
+    appendToVar preFixupPhases qtOwnPathsHook
 
     # Note: $qtWrapperArgs still gets defined even if ${dontWrapQtApps-} is set.
     wrapQtAppsHook() {