diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index fd2f630..7c4a86b 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -4254,7 +4254,7 @@
         arglen = -1;
         argidx = -2;
     }
-    if (Py_TYPE(args)->tp_as_mapping && !PyTuple_Check(args) &&
+    if (PyMapping_Check(args) && !PyTuple_Check(args) &&
         !PyObject_TypeCheck(args, &PyBaseString_Type))
         dict = args;
     while (--fmtcnt >= 0) {