diff --git a/pkgs/build-support/dotnet/build-dotnet-module/hooks/dotnet-fixup-hook.sh b/pkgs/build-support/dotnet/build-dotnet-module/hooks/dotnet-fixup-hook.sh
index 60e1e327274ac..8d4315350ad5b 100644
--- a/pkgs/build-support/dotnet/build-dotnet-module/hooks/dotnet-fixup-hook.sh
+++ b/pkgs/build-support/dotnet/build-dotnet-module/hooks/dotnet-fixup-hook.sh
@@ -97,5 +97,5 @@ dotnetFixupHook() {
 }
 
 if [[ -z "${dontFixup-}" && -z "${dontDotnetFixup-}" ]]; then
-    preFixupPhases+=" dotnetFixupHook"
+    appendToVar preFixupPhases dotnetFixupHook
 fi