diff --git a/src/attributes.js b/src/attributes.js
index abe52b89..5b68773c 100644
--- a/src/attributes.js
+++ b/src/attributes.js
@@ -37,30 +37,31 @@ jQuery.fn.extend({
 	},
 
 	addClass: function( value ) {
+		var classNames, i, l, elem, setClass, c, cl;
+
 		if ( jQuery.isFunction( value ) ) {
-			return this.each(function(i) {
-				var self = jQuery(this);
-				self.addClass( value.call(this, i, self.attr("class") || "") );
+			return this.each(function( j ) {
+				var self = jQuery( this );
+				self.addClass( value.call(this, j, self.attr("class") || "") );
 			});
 		}
 
 		if ( value && typeof value === "string" ) {
-			var classNames = (value || "").split( rspace );
+			classNames = value.split( rspace );
 
-			for ( var i = 0, l = this.length; i < l; i++ ) {
-				var elem = this[i];
+			for ( i = 0, l = this.length; i < l; i++ ) {
+				elem = this[ i ];
 
 				if ( elem.nodeType === 1 ) {
-					if ( !elem.className ) {
+					if ( !elem.className && classNames.length === 1 ) {
 						elem.className = value;
 
 					} else {
-						var className = " " + elem.className + " ",
-							setClass = elem.className;
+						setClass = elem.className;
 
-						for ( var c = 0, cl = classNames.length; c < cl; c++ ) {
-							if ( className.indexOf( " " + classNames[c] + " " ) < 0 ) {
-								setClass += " " + classNames[c];
+						for ( c = 0, cl = classNames.length; c < cl; c++ ) {
+							if ( !~setClass.indexOf(classNames[ c ]) ) {
+								setClass += " " + classNames[ c ];
 							}
 						}
 						elem.className = jQuery.trim( setClass );
@@ -73,24 +74,26 @@ jQuery.fn.extend({
 	},
 
 	removeClass: function( value ) {
-		if ( jQuery.isFunction(value) ) {
-			return this.each(function(i) {
-				var self = jQuery(this);
-				self.removeClass( value.call(this, i, self.attr("class")) );
+		var classNames, i, l, elem, className, c, cl;
+
+		if ( jQuery.isFunction( value ) ) {
+			return this.each(function( j ) {
+				var self = jQuery( this );
+				self.removeClass( value.call(this, j, self.attr("class")) );
 			});
 		}
 
 		if ( (value && typeof value === "string") || value === undefined ) {
-			var classNames = (value || "").split( rspace );
+			classNames = (value || "").split( rspace );
 
-			for ( var i = 0, l = this.length; i < l; i++ ) {
-				var elem = this[i];
+			for ( i = 0, l = this.length; i < l; i++ ) {
+				elem = this[ i ];
 
 				if ( elem.nodeType === 1 && elem.className ) {
 					if ( value ) {
-						var className = (" " + elem.className + " ").replace(rclass, " ");
-						for ( var c = 0, cl = classNames.length; c < cl; c++ ) {
-							className = className.replace(" " + classNames[c] + " ", " ");
+						className = (" " + elem.className + " ").replace( rclass, " " );
+						for ( c = 0, cl = classNames.length; c < cl; c++ ) {
+							className = className.replace(" " + classNames[ c ] + " ", " ");
 						}
 						elem.className = jQuery.trim( className );
 
diff --git a/src/effects.js b/src/effects.js
index 22496277..3a4e2663 100644
--- a/src/effects.js
+++ b/src/effects.js
@@ -15,8 +15,8 @@ var elemdisplay = {},
 	],
 	fxNow,
 	requestAnimationFrame = window.webkitRequestAnimationFrame ||
-	    window.mozRequestAnimationFrame ||
-	    window.oRequestAnimationFrame;
+		window.mozRequestAnimationFrame ||
+		window.oRequestAnimationFrame;
 
 jQuery.fn.extend({
 	show: function( speed, easing, callback ) {
diff --git a/test/data/testsuite.css b/test/data/testsuite.css
index 47caf34a..295740f5 100644
--- a/test/data/testsuite.css
+++ b/test/data/testsuite.css
@@ -119,5 +119,5 @@ sup { display: none; }
 dfn { display: none; }
 
 /* #9239 Attach a background to the body( avoid crashes in removing the test element in support ) */
-body, div { background: url(http://www.ctemploymentlawblog.com/test.jpg) no-repeat -1000px 0; }
+body, div { background: url(http://static.jquery.com/files/rocker/images/logo_jquery_215x53.gif) no-repeat -1000px 0; }
 
diff --git a/test/unit/attributes.js b/test/unit/attributes.js
index 56c398e5..37260f2f 100644
--- a/test/unit/attributes.js
+++ b/test/unit/attributes.js
@@ -761,12 +761,14 @@ test("val(select) after form.reset() (Bug #2551)", function() {
 }); 
 
 var testAddClass = function(valueObj) {
-	expect(5);
+	expect(7);
 	var div = jQuery("div");
 	div.addClass( valueObj("test") );
 	var pass = true;
 	for ( var i = 0; i < div.size(); i++ ) {
-	 if ( div.get(i).className.indexOf("test") == -1 ) pass = false;
+		if ( !~div.get(i).className.indexOf("test") ) {
+			pass = false;
+		}
 	}
 	ok( pass, "Add Class" );
 
@@ -787,6 +789,13 @@ var testAddClass = function(valueObj) {
 	div.attr("class", "foo");
 	div.addClass( valueObj("bar baz") );
 	equals( div.attr("class"), "foo bar baz", "Make sure there isn't too much trimming." );
+	
+	div.removeAttr("class");
+	div.addClass( valueObj("foo") ).addClass( valueObj("foo") )
+	equal( div.attr("class"), "foo", "Do not add the same class twice in separate calls." );
+	div.removeAttr("class");
+	div.addClass( valueObj("bar bar") );
+	equal( div.attr("class"), "bar", "Do not add the same class twice in the same call." );
 };
 
 test("addClass(String)", function() {