diff --git a/lib/transformer.js b/lib/transformer.js
index 989df92..2326c95 100644
--- a/lib/transformer.js
+++ b/lib/transformer.js
@@ -58,7 +58,8 @@ function getAttributeIndex (tag, attr) {
 }
 
 function createClassPrefix(classPrefix) {
-    var re = /\.[\w\-]+/g;
+    //http://stackoverflow.com/questions/12391760/regex-match-css-class-name-from-single-string-containing-multiple-classes
+    var re = /\.(-?[_a-zA-Z]+[_a-zA-Z0-9-]*)(?![^\{]*\})/g;
     var inStyleTag = false;
 
     return function prefixClasses(tag) {
@@ -83,7 +84,17 @@ function createClassPrefix(classPrefix) {
         else {
             var classIdx = getAttributeIndex(tag,'class');
             if(classIdx >= 0) {
-                tag.attributes[classIdx][1] = classPrefix + tag.attributes[classIdx][1];
+                //Prefix classes when multiple classes are present
+                var classes = tag.attributes[classIdx][1];
+                var prefixedClassString = "";
+                
+                classes = classes.replace(/[ ]+/,' ');
+                classes = classes.split(' ');
+                classes.forEach(function(classI){
+                    prefixedClassString += classPrefix + classI + ' ';
+                });
+                
+                tag.attributes[classIdx][1] = prefixedClassString;
             }
         }
         return tag;