diff --git a/cli/tasks/usemin.js b/cli/tasks/usemin.js
index db0e47f4..f8c73c3b 100644
--- a/cli/tasks/usemin.js
+++ b/cli/tasks/usemin.js
@@ -171,7 +171,7 @@ module.exports = function(grunt) {
 
       // actual replacement of revved assets
       if(!!grunt.task._helpers['usemin:post:' + name]) {
-        content = grunt.helper('usemin:post:' + name, content);
+        content = grunt.helper('usemin:post:' + name, content, p);
       }
 
       // write the new content to disk
@@ -350,10 +350,10 @@ module.exports = function(grunt) {
     return content;
   });
 
-  grunt.registerHelper('usemin:post:css', function(content) {
+  grunt.registerHelper('usemin:post:css', function(content, srcPath) {
 
     grunt.log.verbose.writeln('Update the CSS with background imgs, case there is some inline style');
-    content = grunt.helper('replace', content, /url\(\s*['"]?([^'"\)]+)['"]?\s*\)/gm);
+    content = grunt.helper('replace', content, /url\(\s*['"]?([^'"\)]+)['"]?\s*\)/gm, srcPath);
 
     return content;
   });
@@ -363,7 +363,7 @@ module.exports = function(grunt) {
   // regexp should capture the assets relative filepath, it is then compared to
   // the list of files on the filesystem to guess the actual revision of a file
   //
-  grunt.registerHelper('replace', function(content, regexp) {
+  grunt.registerHelper('replace', function(content, regexp, srcPath) {
     return content.replace(regexp, function(match, src) {
       //do not touch external files or the root
       if ( src.match(/\/\//) || src.match(/^\/$/)) {
@@ -377,12 +377,13 @@ module.exports = function(grunt) {
 
       var basename = path.basename(src);
       var dirname = path.dirname(src);
+      var normalizedDirname = path.normalize([path.dirname(srcPath), dirname].join('/'));
 
       // XXX files won't change, the filepath should filter the original list
       // of cached files (we need to treat the filename collision -- i.e. 2 files with same names
       // in different subdirectories)
       var filepaths = grunt.file.expand(path.join('**/*') + basename);
-      var filepath = filepaths.filter(function(f) { return dirname === path.dirname(f);})[0];
+      var filepath = filepaths.filter(function(f) { return normalizedDirname === path.dirname(f); })[0];
 
       // not a file in temp, skip it
       if ( !filepath ) {
diff --git a/cli/test/test-usemin.js b/cli/test/test-usemin.js
index d167d4f8..f073a62c 100644
--- a/cli/test/test-usemin.js
+++ b/cli/test/test-usemin.js
@@ -16,7 +16,7 @@ describe('usemin', function() {
     it("should take into account path", function() {
       usemin.call(grunt,grunt);
 
-      // Let's prepare our context: in index.html we do have references 
+      // Let's prepare our context: in index.html we do have references
       // to images/test.png and images/misc/test.png.
       // Usemin's replace is supposed to change this by files
       // found on the filesystem matching the same path, but
@@ -48,6 +48,15 @@ describe('usemin', function() {
     });
   });
 
+  describe('usemin:post:css', function() {
+    it("should replace img urls in css file", function() {
+      var content = 'url(../images/test.png)';
+      var awaited = 'url(../images/23012.test.png)';
+      var changed = grunt.helper('usemin:post:css', content, 'css/23012.main.css');
+      assert.ok( changed == awaited );
+    });
+  });
+
   describe('usemin:post:html', function() {
     before(function() {
       usemin.call(grunt,grunt);
@@ -55,7 +64,7 @@ describe('usemin', function() {
       grunt.file.mkdir('images');
       grunt.file.mkdir('css');
     });
-  
+
     it('should skip external file', function() {
       grunt.file.write('images/23012.foo.png', "foo");
       var content = '<img src="//css/main.css">';