diff --git a/tests/unit/widget/widget_core.js b/tests/unit/widget/widget_core.js
index 8102b1f4fa8..4aed98fd435 100644
--- a/tests/unit/widget/widget_core.js
+++ b/tests/unit/widget/widget_core.js
@@ -375,6 +375,37 @@ test( "inheritance", function() {
 	delete $.ui.testWidgetExtension;
 });
 
+test( "private methods", function() {
+	expect( 4 );
+
+	$.widget( "ui.testWidgetBase", {
+		publicBase: function()  {
+			deepEqual("a", this._private("__private"), "private method call");
+			deepEqual("b", this._protected(), "protected method call");
+		},
+		_protected: function() { return "a"; },
+		__private: function() { return "a"; }
+	});
+
+	$.widget( "ui.testWidgetExtension", $.ui.testWidgetBase, {
+		publicExt: function() {
+			deepEqual("b", this._private("__private"), "private method call");
+			deepEqual("b", this._protected(), "protected method call");
+		},
+		_protected: function() { return "b"; },
+		__private: function() { return "b"; }
+	});
+
+	var instance = $( "<div>" ).testWidgetExtension();
+	instance.testWidgetExtension("publicBase");
+	instance.testWidgetExtension("publicExt");
+
+	delete $.ui.testWidgetBase;
+	delete $.ui.testWidgetExtension;
+	delete $.fn.testWidgetBase;
+	delete $.fn.testWidgetExtension;
+});
+
 test( "._super()", function() {
 	expect( 9 );
 	var instance;
diff --git a/ui/jquery.ui.autocomplete.js b/ui/jquery.ui.autocomplete.js
index af1acb02b2f..124d89254d1 100644
--- a/ui/jquery.ui.autocomplete.js
+++ b/ui/jquery.ui.autocomplete.js
@@ -428,7 +428,7 @@ $.widget( "ui.autocomplete", {
 
 		return function( content ) {
 			if ( index === requestIndex ) {
-				that.__response( content );
+				that._real_response( content );
 			}
 
 			that.pending--;
@@ -438,7 +438,7 @@ $.widget( "ui.autocomplete", {
 		};
 	},
 
-	__response: function( content ) {
+	_real_response: function( content ) {
 		if ( content ) {
 			content = this._normalize( content );
 		}
@@ -596,7 +596,7 @@ $.widget( "ui.autocomplete", $.ui.autocomplete, {
 		}
 	},
 
-	__response: function( content ) {
+	_real_response: function( content ) {
 		var message;
 		this._superApply( arguments );
 		if ( this.options.disabled || this.cancelSearch ) {
diff --git a/ui/jquery.ui.widget.js b/ui/jquery.ui.widget.js
index c581e4b8156..a2e8ccc8145 100644
--- a/ui/jquery.ui.widget.js
+++ b/ui/jquery.ui.widget.js
@@ -28,6 +28,7 @@ $.widget = function( name, base, prototype ) {
 		// proxiedPrototype allows the provided prototype to remain unmodified
 		// so that it can be used as a mixin for multiple widgets (#8876)
 		proxiedPrototype = {},
+		privatePrototype = {},
 		namespace = name.split( "." )[ 0 ];
 
 	name = name.split( "." )[ 1 ];
@@ -78,29 +79,40 @@ $.widget = function( name, base, prototype ) {
 			proxiedPrototype[ prop ] = value;
 			return;
 		}
-		proxiedPrototype[ prop ] = (function() {
+		var func = (function() {
 			var _super = function() {
 					return base.prototype[ prop ].apply( this, arguments );
 				},
 				_superApply = function( args ) {
 					return base.prototype[ prop ].apply( this, args );
+				},
+				_private = function(prop) {
+					return privatePrototype[ prop ].apply(this, slice.call(arguments, 1));
 				};
 			return function() {
 				var __super = this._super,
 					__superApply = this._superApply,
+					__private = this._private,
 					returnValue;
 
 				this._super = _super;
 				this._superApply = _superApply;
+				this._private = _private;
 
 				returnValue = value.apply( this, arguments );
 
 				this._super = __super;
 				this._superApply = __superApply;
+				this._private = __private;
 
 				return returnValue;
 			};
 		})();
+		if (prop.indexOf("__") === 0) {
+			privatePrototype[prop] = func;
+		} else {
+			proxiedPrototype[ prop ] = func;
+		}
 	});
 	constructor.prototype = $.widget.extend( basePrototype, {
 		// TODO: remove support for widgetEventPrefix