diff --git a/lib/Cake/Test/Case/View/HelperTest.php b/lib/Cake/Test/Case/View/HelperTest.php
index 65d9d8eb5..6cecf1ea1 100644
--- a/lib/Cake/Test/Case/View/HelperTest.php
+++ b/lib/Cake/Test/Case/View/HelperTest.php
@@ -622,6 +622,9 @@ class HelperTest extends CakeTestCase {
 		$result = $this->Helper->assetUrl('style', array('ext' => '.css'));
 		$this->assertEquals('style.css', $result);
 
+		$result = $this->Helper->assetUrl('dir/sub dir/my image', array('ext' => '.jpg'));
+		$this->assertEquals('dir/sub%20dir/my%20image.jpg', $result);
+
 		$result = $this->Helper->assetUrl('foo.jpg?one=two&three=four');
 		$this->assertEquals('foo.jpg?one=two&three=four', $result);
 	}
diff --git a/lib/Cake/View/Helper.php b/lib/Cake/View/Helper.php
index 0eb4eea9d..9e826f215 100644
--- a/lib/Cake/View/Helper.php
+++ b/lib/Cake/View/Helper.php
@@ -313,7 +313,7 @@ class Helper extends Object {
 		if (isset($plugin)) {
 			$path = Inflector::underscore($plugin) . '/' . $path;
 		}
-		$path = h($this->assetTimestamp($this->webroot($path)));
+		$path = $this->_encodeUrl($this->assetTimestamp($this->webroot($path)));
 
 		if (!empty($options['fullBase'])) {
 			$base = $this->url('/', true);
@@ -326,6 +326,21 @@ class Helper extends Object {
 		return $path;
 	}
 
+/**
+ * Encodes a URL for use in HTML attributes.
+ *
+ * @param string $url The url to encode.
+ * @return string The url encoded for both URL & HTML contexts.
+ */
+	protected function _encodeUrl($url) {
+		$path = parse_url($url, PHP_URL_PATH);
+		$encoded = implode('/', array_map(
+			'rawurlencode',
+			explode('/', $path)
+		));
+		return h(str_replace($path, $encoded, $url));
+	}
+
 /**
  * Adds a timestamp to a file based resource based on the value of `Asset.timestamp` in
  * Configure.  If Asset.timestamp is true and debug > 0, or Asset.timestamp == 'force'