diff --git a/mercurial/cext/bdiff.c b/mercurial/cext/bdiff.c
--- a/mercurial/cext/bdiff.c
+++ b/mercurial/cext/bdiff.c
@@ -256,13 +256,12 @@ static int hunk_consumer(int64_t a1, int
 {
 	PyObject *rl = (PyObject *)priv;
 	PyObject *m = Py_BuildValue("LLLL", a1, a2, b1, b2);
+	int r;
 	if (!m)
 		return -1;
-	if (PyList_Append(rl, m) != 0) {
-		Py_DECREF(m);
-		return -1;
-	}
-	return 0;
+	r = PyList_Append(rl, m);
+	Py_DECREF(m);
+	return r;
 }
 
 static PyObject *xdiffblocks(PyObject *self, PyObject *args)