diff --git a/WebLoader/Filter/CssUrlsFilter.php b/WebLoader/Filter/CssUrlsFilter.php
index 3115592..1562453 100644
--- a/WebLoader/Filter/CssUrlsFilter.php
+++ b/WebLoader/Filter/CssUrlsFilter.php
@@ -55,7 +55,7 @@ public function setBasePath($basePath)
 	public function absolutizeUrl($url, $quote, $cssFile)
 	{
 		// is already absolute
-		if (preg_match('/^([a-z]+:\/)?\//', $url)) {
+		if (preg_match('/^([a-z]+:|\/)/i', $url)) {
 			return $url;
 		}
 
@@ -71,7 +71,7 @@ public function absolutizeUrl($url, $quote, $cssFile)
 
 		$path = $this->cannonicalizePath($path);
 
-		return $quote === '"' ? addslashes($path) : $path;
+		return !$quote ? addslashes($path) : $path;
 	}
 
 	/**
@@ -107,30 +107,22 @@ public function cannonicalizePath($path)
 	 */
 	public function __invoke($code, \WebLoader\Compiler $loader, $file = null)
 	{
-		// thanks to kravco
-		$regexp = '~
-			(?<![a-z])
-			url\(                                     ## url(
-				\s*                                   ##   optional whitespace
-				([\'"])?                              ##   optional single/double quote
-				(?!data:)                             ##   keep data URIs
-				(   (?: (?:\\\\.)+                    ##     escape sequences
-					|   [^\'"\\\\,()\s]+              ##     safe characters
-					|   (?(1)   (?!\1)[\'"\\\\,() \t] ##       allowed special characters
-						|       ^                     ##       (none, if not quoted)
-						)
-					)*                                ##     (greedy match)
-				)
-				(?(1)\1)                              ##   optional single/double quote
-				\s*                                   ##   optional whitespace
-			\)                                        ## )
-		~xs';
-
-		$self = $this;
-
-		return preg_replace_callback($regexp, function ($matches) use ($self, $file)
+		$regexp = '/
+			url\(           ## url(
+				\s*             ## optional space
+				([\'"])?        ## optional quote
+				([^\)]+)            ## anything up to ")" character
+				(?(1)\1)        ## optional quote
+				\s*             ## optional space
+			\)              ## )
+		/ix';
+
+		return preg_replace_callback($regexp, function ($matches) use ($file)
 		{
-			return "url('" . $self->absolutizeUrl($matches[2], $matches[1], $file) . "')";
+			$path = trim($matches[2]);	// Remove new lines, spaces, etc
+			$path = trim($path, '\'"');	// Remove quotes on each end (if any)
+
+			return "url('" . $this->absolutizeUrl($path, $matches[1], $file) . "')";
 		}, $code);
 	}
 
diff --git a/tests/Filter/CssUrlsFilterTest.php b/tests/Filter/CssUrlsFilterTest.php
index a5c403c..df67e2d 100644
--- a/tests/Filter/CssUrlsFilterTest.php
+++ b/tests/Filter/CssUrlsFilterTest.php
@@ -2,6 +2,9 @@
 
 namespace WebLoader\Test\Filter;
 
+use WebLoader\Compiler;
+use WebLoader\DefaultOutputNamingConvention;
+use WebLoader\FileCollection;
 use WebLoader\Filter\CssUrlsFilter;
 
 class CssUrlsFilterTest extends \PHPUnit_Framework_TestCase
@@ -12,12 +15,16 @@ class CssUrlsFilterTest extends \PHPUnit_Framework_TestCase
 
 	protected function setUp()
 	{
-		$this->object = new CssUrlsFilter(__DIR__ . '/..', '/');
+		$this->filter = new CssUrlsFilter(__DIR__ . '/..', '/');
+
+		$files = new FileCollection(__DIR__ . '/../fixtures');
+		@mkdir($outputDir = __DIR__ . '/../temp/');
+		$this->compiler = new Compiler($files, new DefaultOutputNamingConvention(), $outputDir);
 	}
 
 	public function testCannonicalizePath()
 	{
-		$path = $this->object->cannonicalizePath('/prase/./dobytek/../ale/nic.jpg');
+		$path = $this->filter->cannonicalizePath('/prase/./dobytek/../ale/nic.jpg');
 		$this->assertEquals('/prase/ale/nic.jpg', $path);
 	}
 
@@ -26,10 +33,16 @@ public function testAbsolutizeAbsolutized()
 		$cssPath = __DIR__ . '/../fixtures/style.css';
 
 		$url = 'http://image.com/image.jpg';
-		$this->assertEquals($url, $this->object->absolutizeUrl($url, '\'', $cssPath));
+		$this->assertEquals($url, $this->filter->absolutizeUrl($url, '\'', $cssPath));
 
 		$abs = '/images/img.png';
-		$this->assertEquals($abs, $this->object->absolutizeUrl($abs, '\'', $cssPath));
+		$this->assertEquals($abs, $this->filter->absolutizeUrl($abs, '\'', $cssPath));
+
+		$abs = 'https://fonts.googleapis.com/css?family=Source+Sans+Pro:300,400,600,700,300italic,400italic,600italic';
+		$this->assertEquals($abs, $this->filter->absolutizeUrl($abs, '\'', $cssPath));
+
+		$abs = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
+		$this->assertEquals($abs, $this->filter->absolutizeUrl($abs, '\'', $cssPath));
 	}
 
 	public function testAbsolutize()
@@ -38,12 +51,12 @@ public function testAbsolutize()
 
 		$this->assertEquals(
 			'/images/image.png',
-			$this->object->absolutizeUrl('./../images/image.png', '\'', $cssPath)
+			$this->filter->absolutizeUrl('./../images/image.png', '\'', $cssPath)
 		);
 
 		$this->assertEquals(
 			'/images/path/to/image.png',
-			$this->object->absolutizeUrl('./../images/path/./to/image.png', '\'', $cssPath)
+			$this->filter->absolutizeUrl('./../images/path/./to/image.png', '\'', $cssPath)
 		);
 	}
 
@@ -51,7 +64,16 @@ public function testAbsolutizeOutsideOfDocRoot()
 	{
 		$path = './../images/image.png';
 		$existingPath = __DIR__ . '/../../Compiler.php';
-		$this->assertEquals($path, $this->object->absolutizeUrl($path, '\'', $existingPath));
+		$this->assertEquals($path, $this->filter->absolutizeUrl($path, '\'', $existingPath));
 	}
 
+	public function testInvoke()
+	{
+		$cssPath = __DIR__ . '/../fixtures/style.css';
+		$code = file_get_contents($cssPath);
+
+		$css = $this->filter->__invoke($code, $this->compiler, $cssPath);
+
+		$this->assertSame(file_get_contents(__DIR__ . '/../fixtures/style.css.expected'), $css);
+	}
 }
diff --git a/tests/fixtures/style.css b/tests/fixtures/style.css
index e69de29..630e745 100644
--- a/tests/fixtures/style.css
+++ b/tests/fixtures/style.css
@@ -0,0 +1,23 @@
+@import url(https://fonts.googleapis.com/css?family=Source+Sans+Pro:300,400,600,700,300italic,400italic,600italic);
+
+body {
+	background: url(img/boxed-bg.jpg);
+}
+
+.greedy-match {
+	background: url("img/\"layer1.jpg"), url('img\'/layer2.jpg');
+}
+
+.addslashes-if-unquoted {
+	background: url(img/'layer1.jpg);
+}
+
+.quote-mismatch {
+	background: url("img/layer2.jpg');
+}
+
+ul {
+	list-style-image: url(
+		data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==
+	);
+}
diff --git a/tests/fixtures/style.css.expected b/tests/fixtures/style.css.expected
new file mode 100644
index 0000000..886497b
--- /dev/null
+++ b/tests/fixtures/style.css.expected
@@ -0,0 +1,21 @@
+@import url('https://fonts.googleapis.com/css?family=Source+Sans+Pro:300,400,600,700,300italic,400italic,600italic');
+
+body {
+	background: url('/fixtures/img/boxed-bg.jpg');
+}
+
+.greedy-match {
+	background: url('/fixtures/img/\"layer1.jpg'), url('/fixtures/img\'/layer2.jpg');
+}
+
+.addslashes-if-unquoted {
+	background: url('/fixtures/img/\'layer1.jpg');
+}
+
+.quote-mismatch {
+	background: url('/fixtures/img/layer2.jpg');
+}
+
+ul {
+	list-style-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==');
+}