diff --git a/src/main/java/com/fasterxml/jackson/databind/ser/std/CalendarSerializer.java b/src/main/java/com/fasterxml/jackson/databind/ser/std/CalendarSerializer.java
index 653d7cf841..559da5b340 100644
--- a/src/main/java/com/fasterxml/jackson/databind/ser/std/CalendarSerializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/ser/std/CalendarSerializer.java
@@ -49,7 +49,8 @@ public void serialize(Calendar value, JsonGenerator jgen, SerializerProvider pro
         } else if (_customFormat != null) {
             // 21-Feb-2011, tatu: not optimal, but better than alternatives:
             synchronized (_customFormat) {
-                jgen.writeString(_customFormat.format(value));
+                // _customformat cannot parse Calendar, so Date should be passed
+                jgen.writeString(_customFormat.format(value.getTime()));
             }
         } else {
             provider.defaultSerializeDateValue(value.getTime(), jgen);