diff --git a/Modules/timemodule.c b/Modules/timemodule.c
index 3ab6e9b..626db3e 100644
--- a/Modules/timemodule.c
+++ b/Modules/timemodule.c
@@ -504,7 +504,7 @@
     fmt = PyBytes_AS_STRING(format);
 #endif
 
-#if defined(MS_WINDOWS)
+#if defined(MS_WINDOWS) && !defined(HAVE_WCSFTIME)
     /* check that the format string contains only valid directives */
     for(outbuf = strchr(fmt, '%');
         outbuf != NULL;
@@ -516,7 +516,8 @@
             !strchr("aAbBcdHIjmMpSUwWxXyYzZ%", outbuf[1]))
         {
             PyErr_SetString(PyExc_ValueError, "Invalid format string");
-            return 0;
+            Py_DECREF(format);
+            return NULL;
         }
     }
 #endif