cdn.fallback.inc |    6 +++---
 cdn.test         |   35 ++++++++++++++++++++++++++---------
 2 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/cdn.fallback.inc b/cdn.fallback.inc
index 55aec64..e682b55 100644
--- a/cdn.fallback.inc
+++ b/cdn.fallback.inc
@@ -24,13 +24,13 @@ function cdn_html_alter_image_urls(&$html) {
   $pattern = "#((<a\s+|<a\s+[^>]*\s+)href\s*=\s*[\"|'])($url_prefix_regex)([^\"|^'|^\?]*)()(\?[^\"|^']*)?";
   $pattern .= "("; // Capture everything after the path.
   $pattern .= "([\"|'][^>]*)>"; // End of opening <a> tag.
-  $pattern .= "((<img\s+|<img\s+[^>]*\s+)src\s*=\s*[\"|'])([^\"|^']*)([\"|'])"; // Wrapped <img> tag.
+  $pattern .= "((<img\s+|<img\s+[^>]*\s+)src\s*=\s*[\"|'])([^\"|^'|^\?]*)()(\?[^\"|^']*)?([\"|'])"; // Wrapped <img> tag.
   $pattern .= ")#i";
-  _cdn_html_alter_file_url($html, $pattern, 0, 4, 5, 1, 7, 11);
+  _cdn_html_alter_file_url($html, $pattern, 0, 4, 6, 1, 7, 11);
 
   // Image file URLs in <img> tags.
   $pattern = "#((<img\s+|<img\s+[^>]*\s+)src\s*=\s*[\"|'])($url_prefix_regex)([^\"|^'|^\?]*)()(\?[^\"|^']*)?([\"|'])#i";
-  _cdn_html_alter_file_url($html, $pattern, 0, 4, 5, 1, 7);
+  _cdn_html_alter_file_url($html, $pattern, 0, 4, 6, 1, 7);
 }
 
 /**
diff --git a/cdn.test b/cdn.test
index 1b292dd..b341d92 100644
--- a/cdn.test
+++ b/cdn.test
@@ -496,24 +496,41 @@ class CDNImageTestCase extends CDNTestCase {
     $html = $template($img_url);
     cdn_html_alter_image_urls($html);
     $this->assertIdentical($template($cdn . $img_url), $html, 'Image HTML correctly altered.');
-    // Query strings should be stripped
-    $html = $template($img_url . '?foobar');
+    // Query strings should not be stripped
+    $img_url = base_path() . 'foo/bar/image.png?foobar';
+    $html = $template($img_url);
+    cdn_html_alter_image_urls($html);
+    $this->assertIdentical($template($cdn . $img_url), $html, 'Image HTML correctly altered (query string not stripped).');
+    // In particular: not the query string used to generate image styles.
+    $img_url = base_path() . 'foo/bar/image.png?itok=1234abcd';
+    $html = $template($img_url);
     cdn_html_alter_image_urls($html);
-    $this->assertIdentical($template($cdn . $img_url), $html, 'Image HTML correctly altered (query string stripped).');
+    $this->assertIdentical($template($cdn . $img_url), $html, 'Image HTML correctly altered (image style query string not stripped).');
     // Edge case: a script generating an image is not (yet) supported.
-    $img_url = base_path() . 'foo/bar/showimage';
-    $html = $template($img_url . '?formula=12345.png');
+    $img_url = base_path() . 'foo/bar/showimage?formula=12345.png';
+    $html = $template($img_url);
     cdn_html_alter_image_urls($html);
-    $this->assertIdentical($template($cdn . $img_url), $html, 'Image HTML correctly altered (query string stripped).');
+    $this->assertIdentical($template($cdn . $img_url), $html, 'Image HTML correctly altered (query string not stripped).');
 
     // Image altering type 2: "linked image", i.e. "<a><img /></a>"..
     $template = function($a_url, $img_url) {
       return '<a href="' . $a_url . '"><img src="' . $img_url . '" /></a>';
     };
-    // Simplest case possible.
+    // Simplest case possible: a linked image linking to the same image.
     $img_base_url = base_path() . 'foo/bar/image';
-    $a_url = $img_base_url . '.png';
-    $img_url = $img_base_url . '-thumbnail.png';
+    $a_url = $img_url = $img_base_url . '.png';
+    $html = $template($a_url, $img_url);
+    cdn_html_alter_image_urls($html);
+    $this->assertIdentical($template($cdn . $a_url, $cdn . $img_url), $html, 'Linked image HTML correctly altered.');
+    // Slightly more complex: a linked image linking to a derivative image.
+    $img_url = $img_base_url . '-thumbnail.png?itok=5678wxyz';
+    $html = $template($a_url, $img_url);
+    cdn_html_alter_image_urls($html);
+    $this->assertIdentical($template($cdn . $a_url, $cdn . $img_url), $html, 'Linked image HTML correctly altered.');
+    // Slightly more complex: a linked derivative image linking to another
+    // derivative image.
+    $a_url = $img_base_url . '-large.png?itok=9012klmn';
+    $img_url = $img_base_url . '-thumbnail.png?itok=5678wxyz';
     $html = $template($a_url, $img_url);
     cdn_html_alter_image_urls($html);
     $this->assertIdentical($template($cdn . $a_url, $cdn . $img_url), $html, 'Linked image HTML correctly altered.');