diff --git a/library/HTMLPurifier/AttrDef.php b/library/HTMLPurifier/AttrDef.php
index 5ac06522..8d4db17f 100644
--- a/library/HTMLPurifier/AttrDef.php
+++ b/library/HTMLPurifier/AttrDef.php
@@ -9,7 +9,6 @@
  * Besides defining (through code) what precisely makes the string valid,
  * subclasses are also responsible for cleaning the code if possible.
  */
-
 abstract class HTMLPurifier_AttrDef
 {
 
@@ -86,7 +85,13 @@ abstract class HTMLPurifier_AttrDef
      */
     protected function mungeRgb($string)
     {
-        return preg_replace('/rgb\((\d+)\s*,\s*(\d+)\s*,\s*(\d+)\)/', 'rgb(\1,\2,\3)', $string);
+        $p = '(\d+(\.\d+)?([%]?))';
+
+        if (preg_match('/(rgba|hsla)\(/', $string)) {
+            return preg_replace('/(rgba|hsla)\(' . $p . '\s*,\s*' . $p . '\s*,\s*' . $p . '\s*,\s*' . $p . '\)/', '\1(\2,\5,\8,\11)', $string);
+        }
+
+        return preg_replace('/(rgb|hsl)\(' . $p . '\s*,\s*' . $p . '\s*,\s*' . $p . '\)/', '\1(\2,\5,\8)', $string);
     }
 
     /**
diff --git a/tests/HTMLPurifier/AttrDef/CSS/BackgroundTest.php b/tests/HTMLPurifier/AttrDef/CSS/BackgroundTest.php
index aa18d096..8d826f87 100644
--- a/tests/HTMLPurifier/AttrDef/CSS/BackgroundTest.php
+++ b/tests/HTMLPurifier/AttrDef/CSS/BackgroundTest.php
@@ -12,12 +12,18 @@ class HTMLPurifier_AttrDef_CSS_BackgroundTest extends HTMLPurifier_AttrDefHarnes
         $this->assertDef($valid);
         $this->assertDef('url(\'chess.png\') #333 50% top repeat fixed', $valid);
         $this->assertDef(
-            'rgb(34, 56, 33) url(chess.png) repeat fixed top',
-            'rgb(34,56,33) url("chess.png") repeat fixed top'
+            'rgb(34%, 56%, 33%) url(chess.png) repeat fixed top',
+            'rgb(34%,56%,33%) url("chess.png") repeat fixed top'
+        );
+        $this->assertDef(
+            'rgba(74, 12, 85, 0.35) repeat fixed bottom',
+            'rgba(74,12,85,.35) repeat fixed bottom'
+        );
+        $this->assertDef(
+            'hsl(244, 47.4%, 88.1%) right center',
+            'hsl(244,47.4%,88.1%) right center'
         );
-
     }
-
 }
 
 // vim: et sw=4 sts=4