diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index b299d48..0b46cee 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -1210,7 +1210,7 @@
 
             if (!errors || strcmp(errors, "strict") == 0) {
                 PyErr_Format(PyExc_ValueError,
-                             "invalid \\x escape at position %d",
+                             "invalid \\x escape at position %zd",
                              s - 2 - (end - len));
                 goto failed;
             }