diff --git a/pandas/tests/series/methods/test_replace.py b/pandas/tests/series/methods/test_replace.py
index 6a8dacfda5e78..68a3844acc338 100644
--- a/pandas/tests/series/methods/test_replace.py
+++ b/pandas/tests/series/methods/test_replace.py
@@ -651,3 +651,15 @@ def test_replace_regex_dtype_series(self, regex):
         expected = pd.Series([1])
         result = series.replace(to_replace="0", value=1, regex=regex)
         tm.assert_series_equal(result, expected)
+
+    def test_replace_different_int_types(self):
+        # GH#45311
+        labs = pd.Series([1, 1, 1, 0, 0, 2, 2, 2]).astype(np.int32)
+
+        maps = pd.Series([np.int64(0), np.int64(2), np.int64(1)])
+        map_dict = {old: new for (old, new) in zip(maps.values, maps.index)}
+
+        result = labs.replace(map_dict)
+        expected = labs.replace({0: 0, 2: 1, 1: 2})
+
+        tm.assert_series_equal(result, expected)