diff --git modules/image/image.module modules/image/image.module
index 23f2e9b..fae5c90 100644
--- modules/image/image.module
+++ modules/image/image.module
@@ -798,16 +798,18 @@ function image_style_flush($style) {
  * @see image_style_deliver()
  */
 function image_style_url($style_name, $path) {
-  $scheme = file_uri_scheme($path);
-  if ($scheme === 'private') {
-    $target = file_uri_target($path);
-    $url = url('system/files/styles/' . $style_name . '/' . $scheme . '/' . $target, array('absolute' => TRUE));
+  $uri = image_style_path($style_name, $path);
+
+  // If not using clean URLs, the image derivative callback is only available
+  // with the query string. If the file does not exist, use url() to ensure
+  // that it is included. Once the file exists it's fine to fall back to the
+  // actual file path, this avoids bootstrapping PHP once the files are built.
+  if (!variable_get('clean_url') && file_uri_scheme($uri) == 'public' && !file_exists($uri)) {
+    $directory_path = file_stream_wrapper_get_instance_by_uri($uri)->getDirectoryPath();
+    return url($directory_path . '/' . file_uri_target($uri), array('absolute' => TRUE));
   }
-  else {
-    $destination = image_style_path($style_name, $path);
-    $url = url(file_stream_wrapper_get_instance_by_scheme($scheme)->getDirectoryPath() . '/' . file_uri_target($destination), array('absolute' => TRUE));
-  }
-  return $url;
+
+  return file_create_url($uri);
 }
 
 /**
@@ -1085,16 +1087,7 @@ function image_effect_apply($image, $effect) {
  * @ingroup themeable
  */
 function theme_image_style($variables) {
-  $style_name = $variables['style_name'];
-  $path = $variables['path'];
-
-  // The derivative image is not created until it has been requested so the file
-  // may not yet exist, in this case we just fallback to the URL.
-  $style_path = image_style_path($style_name, $path);
-  if (!file_exists($style_path)) {
-    $style_path = image_style_url($style_name, $path);
-  }
-  $variables['path'] = $style_path;
+  $variables['path'] = image_style_url($variables['style_name'], $variables['path']);
   return theme('image', $variables);
 }
 
diff --git modules/image/image.test modules/image/image.test
index 7529add..435e41f 100644
--- modules/image/image.test
+++ modules/image/image.test
@@ -156,12 +156,27 @@ class ImageStylesPathAndUrlUnitTest extends DrupalWebTestCase {
   }
 
   /**
+   * Test image_style_url() with the "public://" scheme and unclean URLs.
+   */
+   function testImageStylUrlAndPathPublicUnclean() {
+     $this->_testImageStyleUrlAndPath('public', FALSE);
+   }
+
+  /**
+   * Test image_style_url() with the "private://" schema and unclean URLs.
+   */
+  function testImageStyleUrlAndPathPrivateUnclean() {
+    $this->_testImageStyleUrlAndPath('private', FALSE);
+  }
+
+  /**
    * Test image_style_url().
    */
-  function _testImageStyleUrlAndPath($scheme) {
+  function _testImageStyleUrlAndPath($scheme, $clean_url = TRUE) {
     // 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');
+    variable_set('file_default_schema', $clean_url);
 
     // Create the directories for the styles.
     $directory = $scheme . '://styles/' . $this->style_name;
@@ -183,6 +198,10 @@ class ImageStylesPathAndUrlUnitTest extends DrupalWebTestCase {
     $this->assertFalse(file_exists($generated_uri), t('Generated file does not exist.'));
     $generate_url = image_style_url($this->style_name, $original_uri);
 
+    if (!$clean_url) {
+      $this->assertTrue(strpos($generate_url, '?q=') !== FALSE, 'When using non-clean URLS, the system path contains the query string.');
+    }
+
     // Fetch the URL that generates the file.
     $this->drupalGet($generate_url);
     $this->assertResponse(200, t('Image was generated at the URL.'));