diff --git a/src/iterators.cmod b/src/iterators.cmod
index 7dc7f5c325897f9c5bca6a06e3160cebce58cefa..63edb77e9c20340f751c628388d0e5ffe6941f44 100644
--- a/src/iterators.cmod
+++ b/src/iterators.cmod
@@ -319,8 +319,8 @@ PIKECLASS mapping_iterator
   {
     if (THIS->md) {
       push_int(THIS->md->size);
-    }
-    push_undefined();
+    } else
+      push_undefined();
   }
 
 #ifdef PIKE_MAPPING_KEYPAIR_LOOP