diff --git a/lib/trivial.nix b/lib/trivial.nix
index 5d4fad8266bc..0e02660d6b35 100644
--- a/lib/trivial.nix
+++ b/lib/trivial.nix
@@ -514,6 +514,8 @@ rec {
           in
             [r] ++ go q;
     in
+      assert (isInt base);
+      assert (isInt i);
       assert (base >= 2);
       assert (i >= 0);
       lib.reverseList (go i);