diff --git a/modules/image/image.module b/modules/image/image.module
index b3ba7c4..88fe429 100644
--- a/modules/image/image.module
+++ b/modules/image/image.module
@@ -1010,10 +1010,14 @@ function image_style_flush($style) {
  */
 function image_style_url($style_name, $path) {
   $uri = image_style_path($style_name, $path);
+
+  // The passed-in $path variable can be either a relative path or a full URI.
+  $original_uri = file_uri_scheme($path) ? file_stream_wrapper_uri_normalize($path) : file_build_uri($path);
+
   // The token query is added even if the 'image_allow_insecure_derivatives'
   // variable is TRUE, so that the emitted links remain valid if it is changed
   // back to the default FALSE.
-  $token_query = array(IMAGE_DERIVATIVE_TOKEN => image_style_path_token($style_name, file_stream_wrapper_uri_normalize($path)));
+  $token_query = array(IMAGE_DERIVATIVE_TOKEN => image_style_path_token($style_name, $original_uri));
 
   // If not using clean URLs, the image derivative callback is only available
   // with the query string. If the file does not exist, use url() to ensure
diff --git a/modules/image/image.test b/modules/image/image.test
index 7db68e6..dadb46c 100644
--- a/modules/image/image.test
+++ b/modules/image/image.test
@@ -221,6 +221,16 @@ class ImageStylesPathAndUrlTestCase extends DrupalWebTestCase {
     $this->drupalGet(str_replace(IMAGE_DERIVATIVE_TOKEN . '=', 'wrongparam=', $generate_url));
     $this->assertResponse(403, 'Image was inaccessible at the URL wih a missing token.');
 
+    // Check that the generated URL is the same when we pass in a relative path
+    // rather than a URI. We need to temporarily switch the default scheme to
+    // match the desired scheme before testing this, then switch it back to the
+    // "temporary" scheme used throughout this test afterwards.
+    variable_set('file_default_scheme', $scheme);
+    $relative_path = file_uri_target($original_uri);
+    $generate_url_from_relative_path = image_style_url($this->style_name, $relative_path);
+    $this->assertEqual($generate_url, $generate_url_from_relative_path, 'Generated URL is the same regardless of whether it came from a relative path or a file URI.');
+    variable_set('file_default_scheme', 'temporary');
+
     // Fetch the URL that generates the file.
     $this->drupalGet($generate_url);
     $this->assertResponse(200, 'Image was generated at the URL.');