diff --git a/pandas/indexes/multi.py b/pandas/indexes/multi.py
index 3f84d8b292980..74c45aac8b620 100644
--- a/pandas/indexes/multi.py
+++ b/pandas/indexes/multi.py
@@ -1224,6 +1224,7 @@ def _sort_levels_monotonic(self):
             lev = lev.take(indexer)
 
             # indexer to reorder the labels
+            indexer = _ensure_int64(indexer)
             ri = lib.get_reverse_indexer(indexer, len(indexer))
             lab = algos.take_1d(ri, lab)