diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 3da40dd..cdfc2f6 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -13948,7 +13948,7 @@
     UNICODE_ISIDENTIFIER_METHODDEF
     UNICODE_ISPRINTABLE_METHODDEF
     UNICODE_ZFILL_METHODDEF
-    {"format", (PyCFunction) do_string_format, METH_VARARGS | METH_KEYWORDS, format__doc__},
+    {"format", (PyCFunction)(void(*)(void)) do_string_format, METH_VARARGS | METH_KEYWORDS, format__doc__},
     {"format_map", (PyCFunction) do_string_format_map, METH_O, format_map__doc__},
     UNICODE___FORMAT___METHODDEF
     UNICODE_MAKETRANS_METHODDEF