diff --git a/Modules/stropmodule.c b/Modules/stropmodule.c
index 234a4dd..4b8a501 100644
--- a/Modules/stropmodule.c
+++ b/Modules/stropmodule.c
@@ -818,7 +818,7 @@
 		x = (long) PyOS_strtoul(s, &end, base);
 	else
 		x = PyOS_strtol(s, &end, base);
-	if (end == s || !isxdigit(end[-1]))
+	if (end == s || !isalnum(end[-1]))
 		goto bad;
 	while (*end && isspace(Py_CHARMASK(*end)))
 		end++;