diff --git a/src/ajax/ajax.js b/src/ajax/ajax.js
index 4f0b2e8fd..d9b3a3d8b 100644
--- a/src/ajax/ajax.js
+++ b/src/ajax/ajax.js
@@ -434,7 +434,7 @@ jQuery.extend({
 	 * @cat Ajax
 	 */
 	ajaxSetup: function( settings ) {
-		jQuery.extend( jQuery.ajaxSettings, settings );
+		jQuery.extend( true, jQuery.ajaxSettings, settings );
 	},
 
 	ajaxSettings: {
@@ -575,7 +575,7 @@ jQuery.extend({
 	ajax: function( s ) {
 		// Extend the settings, but re-extend 's' so that it can be
 		// checked again later (in the test suite, specifically)
-		s = jQuery.extend(s, jQuery.extend({}, jQuery.ajaxSettings, s));
+		s = jQuery.extend(true, s, jQuery.extend(true, {}, jQuery.ajaxSettings, s));
 
 		// if data available
 		if ( s.data ) {
diff --git a/src/jquery/coreTest.js b/src/jquery/coreTest.js
index ff8909c8b..312bc3ce1 100644
--- a/src/jquery/coreTest.js
+++ b/src/jquery/coreTest.js
@@ -680,7 +680,7 @@ test("$.extend(Object, Object)", function() {
 	isObj( settings, merged, "Check if extended: settings must be extended" );
 	isObj( options, optionsCopy, "Check if not modified: options must not be modified" );
 
-	jQuery.extend(deep1, deep2);
+	jQuery.extend(true, deep1, deep2);
 	isObj( deep1.foo, deepmerged.foo, "Check if foo: settings must be extended" );
 	isObj( deep2.foo, deep2copy.foo, "Check if not deep2: options must not be modified" );
 
diff --git a/src/jquery/jquery.js b/src/jquery/jquery.js
index 797280e07..a79b2e6b2 100644
--- a/src/jquery/jquery.js
+++ b/src/jquery/jquery.js
@@ -1256,7 +1256,13 @@ jQuery.fn = jQuery.prototype = {
  */
 jQuery.extend = jQuery.fn.extend = function() {
 	// copy reference to target object
-	var target = arguments[0] || {}, a = 1, al = arguments.length;
+	var target = arguments[0] || {}, a = 1, al = arguments.length, deep = false;
+
+	// Handle a deep copy situation
+	if ( target.constructor == Boolean ) {
+		deep = true;
+		target = arguments[1] || {};
+	}
 
 	// extend jQuery itself if only one argument is passed
 	if ( al == 1 ) {
@@ -1276,7 +1282,7 @@ jQuery.extend = jQuery.fn.extend = function() {
 					continue;
 
 				// Recurse if we're merging object values
-				if ( typeof prop[i] == 'object' && target[i] )
+				if ( deep && typeof prop[i] == 'object' && target[i] )
 					jQuery.extend( target[i], prop[i] );
 
 				// Don't bring in undefined values