Issue #9566: use Py_ssize_t instead of int
diff --git a/Objects/listobject.c b/Objects/listobject.c
index bcc6bc0..2e0c8aa 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -1381,7 +1381,7 @@
 
 /* Conceptually a MergeState's constructor. */
 static void
-merge_init(MergeState *ms, int list_size, int has_keyfunc)
+merge_init(MergeState *ms, Py_ssize_t list_size, int has_keyfunc)
 {
     assert(ms != NULL);
     if (has_keyfunc) {