diff --git a/Objects/stringlib/string_format.h b/Objects/stringlib/string_format.h
index 2799141..4ae7e57 100644
--- a/Objects/stringlib/string_format.h
+++ b/Objects/stringlib/string_format.h
@@ -416,6 +416,7 @@
             Py_DECREF(key);
             goto error;
         }
+        Py_INCREF(obj);
     } else {
         /* look up in args */
         obj = PySequence_GetItem(args, index);