diff --git a/lib/modules.nix b/lib/modules.nix
index c67ea2247ca7..054f18a004f3 100644
--- a/lib/modules.nix
+++ b/lib/modules.nix
@@ -1320,13 +1320,24 @@ let
     : 1\. Function argument
   */
   pushDownProperties =
+    let
+      mapAttrsIfAttrs =
+        f: val:
+        if isAttrs val then
+          mapAttrs f val
+        else
+          # This does not actually work, since arriving here means we have e.g.
+          # (lib.mkIf cond nonAttrs), while an attrset is expected. However,
+          # avoiding the mapAttrs call here gives better errors later.
+          val;
+    in
     cfg:
     if cfg._type or "" == "merge" then
       concatMap pushDownProperties cfg.contents
     else if cfg._type or "" == "if" then
-      map (mapAttrs (n: v: mkIf cfg.condition v)) (pushDownProperties cfg.content)
+      map (mapAttrsIfAttrs (n: v: mkIf cfg.condition v)) (pushDownProperties cfg.content)
     else if cfg._type or "" == "override" then
-      map (mapAttrs (n: v: mkOverride cfg.priority v)) (pushDownProperties cfg.content)
+      map (mapAttrsIfAttrs (n: v: mkOverride cfg.priority v)) (pushDownProperties cfg.content)
     # FIXME: handle mkOrder?
     else
       [ cfg ];