diff --git a/tests/test_jsonable_encoder.py b/tests/test_jsonable_encoder.py
index cdd3a47b5..e2319221b 100644
--- a/tests/test_jsonable_encoder.py
+++ b/tests/test_jsonable_encoder.py
@@ -216,6 +216,11 @@ def test_custom_encoders():
     )
     assert encoded_instance["dt_field"] == instance["dt_field"].strftime("%H:%M:%S")
 
+    encoded_instance = jsonable_encoder(
+        instance, custom_encoder={datetime: lambda o: o.strftime("%H:%M:%S")}
+    )
+    assert encoded_instance["dt_field"] == instance["dt_field"].strftime("%H:%M:%S")
+
     encoded_instance2 = jsonable_encoder(instance)
     assert encoded_instance2["dt_field"] == instance["dt_field"].isoformat()