diff --git a/modules/nix/nixpkgs.nix b/modules/nix/nixpkgs.nix
index f1998071..dc95f919 100644
--- a/modules/nix/nixpkgs.nix
+++ b/modules/nix/nixpkgs.nix
@@ -30,7 +30,11 @@ let
 
   configType = mkOptionType {
     name = "nixpkgs config";
-    check = traceValIfNot isConfig;
+    check = x:
+      let traceXIfNot = c:
+            if c x then true
+            else lib.traceSeqN 1 x false;
+      in traceXIfNot isConfig;
     merge = args: fold (def: mergeConfig def.value) {};
   };