diff --git a/lib/customisation.nix b/lib/customisation.nix
index fdaf80c9b6b8..f20298cb8808 100644
--- a/lib/customisation.nix
+++ b/lib/customisation.nix
@@ -168,8 +168,8 @@ rec {
             f
             // fDecorated
             # Decorate f.override if presented
-            // lib.optionalAttrs (f ? override) {
-              override = fdrv: makeOverridable (f.override fdrv);
+            // {
+              ${if f ? override then "override" else null} = fdrv: makeOverridable (f.override fdrv);
             }
           )
             (mirrorArgs f')