diff --git a/src/selector.js b/src/selector.js
index 505198b23..c97ba61ff 100644
--- a/src/selector.js
+++ b/src/selector.js
@@ -165,7 +165,8 @@ Sizzle.find = function(expr, context, isXML){
 };
 
 Sizzle.filter = function(expr, set, inplace, not){
-	var old = expr, result = [], curLoop = set, match, anyFound;
+	var old = expr, result = [], curLoop = set, match, anyFound,
+		isXMLFilter = set && set[0] && isXML(set[0]);
 
 	while ( expr && set.length ) {
 		for ( var type in Expr.filter ) {
@@ -178,7 +179,7 @@ Sizzle.filter = function(expr, set, inplace, not){
 				}
 
 				if ( Expr.preFilter[ type ] ) {
-					match = Expr.preFilter[ type ]( match, curLoop, inplace, result, not );
+					match = Expr.preFilter[ type ]( match, curLoop, inplace, result, not, isXMLFilter );
 
 					if ( !match ) {
 						anyFound = found = true;
@@ -357,9 +358,13 @@ var Expr = Sizzle.selectors = {
 		}
 	},
 	preFilter: {
-		CLASS: function(match, curLoop, inplace, result, not){
+		CLASS: function(match, curLoop, inplace, result, not, isXML){
 			match = " " + match[1].replace(/\\/g, "") + " ";
 
+			if ( isXML ) {
+				return match;
+			}
+
 			for ( var i = 0, elem; (elem = curLoop[i]) != null; i++ ) {
 				if ( elem ) {
 					if ( not ^ (elem.className && (" " + elem.className + " ").indexOf(match) >= 0) ) {
@@ -397,10 +402,10 @@ var Expr = Sizzle.selectors = {
 
 			return match;
 		},
-		ATTR: function(match){
+		ATTR: function(match, curLoop, inplace, result, not, isXML){
 			var name = match[1].replace(/\\/g, "");
 			
-			if ( Expr.attrMap[name] ) {
+			if ( !isXML && Expr.attrMap[name] ) {
 				match[1] = Expr.attrMap[name];
 			}
 
@@ -588,7 +593,8 @@ var Expr = Sizzle.selectors = {
 			return (match === "*" && elem.nodeType === 1) || elem.nodeName === match;
 		},
 		CLASS: function(elem, match){
-			return match.test( elem.className );
+			return (" " + (elem.className || elem.getAttribute("class")) + " ")
+				.indexOf( match ) > -1;
 		},
 		ATTR: function(elem, match){
 			var name = match[1],
@@ -815,8 +821,10 @@ if ( document.getElementsByClassName && document.documentElement.getElementsByCl
 		return;
 
 	Expr.order.splice(1, 0, "CLASS");
-	Expr.find.CLASS = function(match, context) {
-		return context.getElementsByClassName(match[1]);
+	Expr.find.CLASS = function(match, context, isXML) {
+		if ( typeof context.getElementsByClassName !== "undefined" && !isXML ) {
+			return context.getElementsByClassName(match[1]);
+		}
 	};
 })();
 
diff --git a/test/data/test.js b/test/data/test.js
index 403d0d45d..a41cb232b 100644
--- a/test/data/test.js
+++ b/test/data/test.js
@@ -1,3 +1,3 @@
-foobar = "bar";
+var foobar = "bar";
 jQuery('#ap').html('bar');
 ok( true, "test.js executed");
diff --git a/test/data/test2.html b/test/data/test2.html
index dec2b5d9f..1df6151a0 100644
--- a/test/data/test2.html
+++ b/test/data/test2.html
@@ -1,5 +1,5 @@
 <script type="text/javascript">
-testFoo = "foo";
+var testFoo = "foo";
 jQuery('#foo').html('foo');
 ok( true, "test2.html executed" );
 </script>
diff --git a/test/data/with_fries.xml b/test/data/with_fries.xml
index 88e0e49d5..42f425706 100644
--- a/test/data/with_fries.xml
+++ b/test/data/with_fries.xml
@@ -6,7 +6,7 @@
 		<jsconf xmlns="http://www.example.com/ns1">
 			<response xmlns:ab="http://www.example.com/ns2">
 				<meta>
-					<component id="seite1">
+					<component id="seite1" class="component">
 						<properties xmlns:cd="http://www.example.com/ns3">
 							<property name="prop1">
 								<thing />
diff --git a/test/unit/selector.js b/test/unit/selector.js
index 9f29bf6bf..c4c13601b 100644
--- a/test/unit/selector.js
+++ b/test/unit/selector.js
@@ -35,10 +35,12 @@ test("element", function() {
 
 if ( location.protocol != "file:" ) {
 	test("XML Document Selectors", function() {
-		expect(5);
+		expect(7);
 		stop();
 		jQuery.get("data/with_fries.xml", function(xml) {
 			equals( jQuery("foo_bar", xml).length, 1, "Element Selector with underscore" );
+			equals( jQuery(".component", xml).length, 1, "Class selector" );
+			equals( jQuery("[class*=component]", xml).length, 1, "Attribute selector for class" );
 			equals( jQuery("property[name=prop2]", xml).length, 1, "Attribute selector with name" );
 			equals( jQuery("[name=prop2]", xml).length, 1, "Attribute selector with name" );
 			equals( jQuery("#seite1", xml).length, 1, "Attribute selector with ID" );