diff --git a/tests/unit/widget/widget_core.js b/tests/unit/widget/widget_core.js
index 0296b9e4f..5efd91268 100644
--- a/tests/unit/widget/widget_core.js
+++ b/tests/unit/widget/widget_core.js
@@ -83,7 +83,7 @@ test( "custom selector expression", function() {
 	var elem = $( "<div>" ).appendTo( "#qunit-fixture" );
 	$.widget( "ui.testWidget", {} );
 	elem.testWidget();
-	deepEqual( $( ":ui-testWidget" )[0], elem[0] );
+	deepEqual( $( ":ui-testwidget" )[0], elem[0] );
 	elem.testWidget( "destroy" );
 });
 
diff --git a/ui/jquery.ui.widget.js b/ui/jquery.ui.widget.js
index 628b63bb0..b5dfaa344 100644
--- a/ui/jquery.ui.widget.js
+++ b/ui/jquery.ui.widget.js
@@ -36,7 +36,7 @@ $.widget = function( name, base, prototype ) {
 	}
 
 	// create selector for plugin
-	$.expr[ ":" ][ fullName ] = function( elem ) {
+	$.expr[ ":" ][ fullName.toLowerCase() ] = function( elem ) {
 		return !!$.data( elem, fullName );
 	};