diff --git a/modules/image/image.module b/modules/image/image.module
index 258f12f..78f5eff 100644
--- a/modules/image/image.module
+++ b/modules/image/image.module
@@ -993,7 +993,7 @@ function image_style_url($style_name, $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, $path));
+  $token_query = array(IMAGE_DERIVATIVE_TOKEN => image_style_path_token($style_name, file_stream_wrapper_uri_normalize($path)));
 
   // 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 d4db213..1577d44 100644
--- a/modules/image/image.test
+++ b/modules/image/image.test
@@ -168,9 +168,16 @@ class ImageStylesPathAndUrlTestCase extends DrupalWebTestCase {
   }
 
   /**
+   * Test image_style_url() with a file URL that has an extra slash in it.
+   */
+  function testImageStyleUrlExtraSlash() {
+    $this->_testImageStyleUrlAndPath('public', TRUE, TRUE);
+  }
+
+  /**
    * Test image_style_url().
    */
-  function _testImageStyleUrlAndPath($scheme, $clean_url = TRUE) {
+  function _testImageStyleUrlAndPath($scheme, $clean_url = TRUE, $extra_slash = FALSE) {
     // Make the default scheme neither "public" nor "private" to verify the
     // functions work for other than the default scheme.
     variable_set('file_default_scheme', 'temporary');
@@ -196,6 +203,15 @@ class ImageStylesPathAndUrlTestCase extends DrupalWebTestCase {
     $this->assertFalse(file_exists($generated_uri), t('Generated file does not exist.'));
     $generate_url = image_style_url($this->style_name, $original_uri);
 
+    // Ensure that the tests still pass when the file is generated by accessing
+    // a poorly constructed (but still valid) file URL that has an extra slash
+    // in it.
+    if ($extra_slash) {
+      $modified_uri = str_replace('://', ':///', $original_uri);
+      $this->assertNotEqual($original_uri, $modified_uri, 'An extra slash was added to the generated file URI.');
+      $generate_url = image_style_url($this->style_name, $modified_uri);
+    }
+
     if (!$clean_url) {
       $this->assertTrue(strpos($generate_url, '?q=') !== FALSE, 'When using non-clean URLS, the system path contains the query string.');
     }