diff --git a/src/RangeCalendar.js b/src/RangeCalendar.js
index 0c2f938da..6f10f9383 100644
--- a/src/RangeCalendar.js
+++ b/src/RangeCalendar.js
@@ -102,7 +102,7 @@ class RangeCalendar extends React.Component {
     onValueChange: PropTypes.func,
     onHoverChange: PropTypes.func,
     onPanelChange: PropTypes.func,
-    format: PropTypes.oneOfType([PropTypes.object, PropTypes.string]),
+    format: PropTypes.any,
     onClear: PropTypes.func,
     type: PropTypes.any,
     disabledDate: PropTypes.func,