diff --git a/mercurial/cext/bdiff.c b/mercurial/cext/bdiff.c
--- a/mercurial/cext/bdiff.c
+++ b/mercurial/cext/bdiff.c
@@ -257,7 +257,8 @@ abort:
 	return NULL;
 }
 
-static int hunk_consumer(long a1, long a2, long b1, long b2, void *priv)
+static int hunk_consumer(int64_t a1, int64_t a2, int64_t b1, int64_t b2,
+                         void *priv)
 {
 	PyObject *rl = (PyObject *)priv;
 	PyObject *m = Py_BuildValue("llll", a1, a2, b1, b2);