diff --git a/ui/datepicker.js b/ui/datepicker.js
index 735866c39..10b7d7eb5 100644
--- a/ui/datepicker.js
+++ b/ui/datepicker.js
@@ -139,6 +139,8 @@ function Datepicker() {
 		disabled: false // The initial disabled state
 	};
 	$.extend(this._defaults, this.regional[""]);
+	this.regional.en = $.extend( true, {}, this.regional[ "" ]);
+	this.regional[ "en-US" ] = $.extend( true, {}, this.regional.en );
 	this.dpDiv = datepicker_bindHover($("<div id='" + this._mainDivId + "' class='ui-datepicker ui-widget ui-widget-content ui-helper-clearfix ui-corner-all'></div>"));
 }