diff --git a/cdn.basic.css.inc b/cdn.basic.css.inc
index 30c1e50..e20b0a6 100644
--- a/cdn.basic.css.inc
+++ b/cdn.basic.css.inc
@@ -12,6 +12,12 @@
  * Mostly based on drupal_get_css().
  */
 function _cdn_css_aggregate(&$vars) {
+  // Don't override Drupal core's aggregation if this page is not going to use
+  // a CDN anyway.
+  if (!cdn_check_protocol() && !cdn_check_drupal_path($_GET['q'])) {
+    return;
+  }
+
   $output = '';
   $prefix = $suffix = '<!-- CSS aggregated by CDN module. -->' . "\n";
 
@@ -20,6 +26,7 @@ function _cdn_css_aggregate(&$vars) {
   $no_module_preprocess = '';
   $no_theme_preprocess = '';
 
+  $query_string = variable_get('css_js_query_string', '0');
   $preprocess_css = (variable_get('preprocess_css', FALSE) && (!defined('MAINTENANCE_MODE') || MAINTENANCE_MODE != 'update'));
   $directory = file_directory_path();
   $is_writable = is_dir($directory) && is_writable($directory) && (variable_get('file_downloads', FILE_DOWNLOADS_PUBLIC) == FILE_DOWNLOADS_PUBLIC);
@@ -46,18 +53,24 @@ function _cdn_css_aggregate(&$vars) {
         // Only include the stylesheet if it exists.
         if (file_exists($file)) {
           if (!$preprocess || !($is_writable && $preprocess_css)) {
+            // Also build CSS cache files for other files; so that the file
+            // URLs in them are altered to point to the CDN.
+            $fake_types = array($type => array($file => TRUE));
+            $filename = 'cdn_css_' . md5(serialize($types) . $query_string . 'cdn') .'_'. basename($file);
+            $file = _cdn_build_css_cache($fake_types, $filename);
+
             // If a CSS file is not to be preprocessed and it's a module CSS file, it needs to *always* appear at the *top*,
             // regardless of whether preprocessing is on or off.
             if (!$preprocess && $type == 'module') {
-              $no_module_preprocess .= '<link type="text/css" rel="stylesheet" media="'. $media .'" href="'. file_create_url($file) .'" />'."\n";
+              $no_module_preprocess .= '<link type="text/css" rel="stylesheet" media="'. $media .'" href="'. _cdn_css_file_create_url($file) .'" />'."\n";
             }
             // If a CSS file is not to be preprocessed and it's a theme CSS file, it needs to *always* appear at the *bottom*,
             // regardless of whether preprocessing is on or off.
             else if (!$preprocess && $type == 'theme') {
-              $no_theme_preprocess .= '<link type="text/css" rel="stylesheet" media="'. $media .'" href="'. file_create_url($file) .'" />'."\n";
+              $no_theme_preprocess .= '<link type="text/css" rel="stylesheet" media="'. $media .'" href="'. _cdn_css_file_create_url($file) .'" />'."\n";
             }
             else {
-              $output .= '<link type="text/css" rel="stylesheet" media="'. $media .'" href="'. file_create_url($file) .'" />'."\n";
+              $output .= '<link type="text/css" rel="stylesheet" media="'. $media .'" href="'. _cdn_css_file_create_url($file) .'" />'."\n";
             }
           }
         }
@@ -67,10 +80,9 @@ function _cdn_css_aggregate(&$vars) {
     if ($is_writable && $preprocess_css) {
       // Prefix filename to prevent blocking by firewalls which reject files
       // starting with "ad*".
-      $query_string = variable_get('css_js_query_string', '0');
-      $filename = 'css_'. md5(serialize($types) . $query_string . 'cdn') .'.css';
+      $filename = 'cdn_css_'. md5(serialize($types) . $query_string . 'cdn') .'.css';
       $preprocess_file = _cdn_build_css_cache($types, $filename);
-      $output .= '<link type="text/css" rel="stylesheet" media="'. $media .'" href="'. file_create_url($preprocess_file) .'" />'."\n";
+      $output .= '<link type="text/css" rel="stylesheet" media="'. $media .'" href="'. _cdn_css_file_create_url($preprocess_file) .'" />'."\n";
     }
   }
 
@@ -127,5 +139,27 @@ function _cdn_build_css_path($matches, $base = NULL) {
     $path = preg_replace('`(^|/)(?!\.\./)([^/]+)/\.\./`', '$1', $path);
   }
 
-  return 'url('. file_create_url($path) .')';
+  return 'url('. _cdn_css_file_create_url($path) .')';
+}
+
+/**
+ * Generate CDN file URL without file_create_url() if the core patch has not
+ * been applied.
+ */
+function _cdn_css_file_create_url($path) {
+  if (variable_get(CDN_THEME_LAYER_FALLBACK_VARIABLE, FALSE) == TRUE) {
+    // Store the current path as the old path, then let cdn_file_url_alter()
+    // do its magic by invoking all file_url_alter hooks. When the path hasn't
+    // changed and is not already root-relative or protocol-relative, then
+    // generate a file URL as Drupal core would: prepend the base path.
+    $old_path = $path;
+    drupal_alter('file_url', $path);
+    if ($path == $old_path && drupal_substr($path, 0, 1) != '/' && drupal_substr($path, 0, 2) != '//') {
+      $path = base_path() . $path;
+    }
+    return $path;
+  }
+  else {
+    return file_create_url($path);
+  }
 }
diff --git a/cdn.module b/cdn.module
index 8e66b7a..ab256cc 100644
--- a/cdn.module
+++ b/cdn.module
@@ -70,15 +70,9 @@ function cdn_file_url_alter(&$path) {
   $mode                  = variable_get(CDN_MODE_VARIABLE, CDN_MODE_BASIC);
   $farfuture             = variable_get(CDN_BASIC_FARFUTURE_VARIABLE, CDN_BASIC_FARFUTURE_DEFAULT);
   $stats                 = variable_get(CDN_STATS_VARIABLE, FALSE) && user_access(CDN_PERM_ACCESS_STATS);
-  $file_path_blacklist   = variable_get(CDN_EXCEPTION_FILE_PATH_BLACKLIST_VARIABLE, CDN_EXCEPTION_FILE_PATH_BLACKLIST_DEFAULT);
-  $file_path_whitelist   = variable_get(CDN_EXCEPTION_FILE_PATH_WHITELIST_VARIABLE, CDN_EXCEPTION_FILE_PATH_WHITELIST_DEFAULT);
-  $drupal_path_blacklist = variable_get(CDN_EXCEPTION_DRUPAL_PATH_BLACKLIST_VARIABLE, CDN_EXCEPTION_DRUPAL_PATH_BLACKLIST_DEFAULT);
-  $auth_users_blacklist  = variable_get(CDN_EXCEPTION_AUTH_USERS_BLACKLIST_VARIABLE, CDN_EXCEPTION_AUTH_USERS_BLACKLIST_DEFAULT);
   $https_support         = variable_get(CDN_HTTPS_SUPPORT_VARIABLE, FALSE);
   $maintenance_mode      = variable_get('maintenance_mode', FALSE);
   $is_https_page         = cdn_request_is_https();
-  $module_blacklist      = cdn_get_blacklist();
-  global $user;
 
   // Don't alter file URLs when running update.php.
   if (defined('MAINTENANCE_MODE')) {
@@ -92,35 +86,13 @@ function cdn_file_url_alter(&$path) {
       return;
     }
 
-    // If the current page is being served via HTTPS, and the CDN does not
-    // support HTTPS, then don't rewrite the file URL, because it would make the
-    // visit insecure.
-    if ($is_https_page && !$https_support) {
+    if (!cdn_check_protocol()) {
       return;
     }
-
-    // If the current file path matches one of the blacklisted file paths,
-    // return immediately, except when the current file path also matches one
-    // of the whitelisted file paths.
-    if ((
-          drupal_match_path($path, $file_path_blacklist)
-          ||
-          drupal_match_path($path, $module_blacklist)
-        )
-        && !drupal_match_path($path, $file_path_whitelist)
-      )
-    {
-        return;
-    }
-
-    // If the current Drupal path matches one of the blacklisted Drupal paths,
-    // return immediately.
-    if (drupal_match_path($_GET['q'], $drupal_path_blacklist)) {
+    if (!cdn_check_drupal_path($_GET['q'])) {
       return;
     }
-
-    // If logged in user, apply a secondary blacklist.
-    if ($user->uid > 0 && drupal_match_path($_GET['q'], $auth_users_blacklist)) {
+    if (!cdn_check_file($path)) {
       return;
     }
 
@@ -690,6 +662,76 @@ function cdn_request_is_https() {
 }
 
 /**
+ * Check if the current protocol is supported by the CDN.
+ *
+ * Note: currently only checks HTTPS, in the future possibly also SPDY.
+ */
+function cdn_check_protocol() {
+  $https_support = variable_get(CDN_HTTPS_SUPPORT_VARIABLE, FALSE);
+
+  // If the current page is being served via HTTPS, and the CDN does not
+  // support HTTPS, then don't rewrite the file URL, because it would make the
+  // visit insecure.
+  if (cdn_request_is_https() && !$https_support) {
+    return FALSE;
+  }
+
+  return TRUE;
+}
+
+/**
+ * Check if a Drupal path should serve files from the CDN (i.e.: is the Drupal
+ * path blacklisted?).
+ *
+ * @param $path
+ *   A Drupal path.
+ */
+function cdn_check_drupal_path($path) {
+  global $user;
+  $blacklist       = variable_get(CDN_EXCEPTION_DRUPAL_PATH_BLACKLIST_VARIABLE, CDN_EXCEPTION_DRUPAL_PATH_BLACKLIST_DEFAULT);
+  $auth_blacklist  = variable_get(CDN_EXCEPTION_AUTH_USERS_BLACKLIST_VARIABLE, CDN_EXCEPTION_AUTH_USERS_BLACKLIST_DEFAULT);
+
+  // Check if the Drupal path matches one of the blacklisted Drupal paths.
+  if (drupal_match_path($path, $blacklist)) {
+    return FALSE;
+  }
+
+  // If logged in user, apply a secondary blacklist.
+  if ($user->uid > 0 && drupal_match_path($path, $auth_blacklist)) {
+    return FALSE;
+  }
+
+  return TRUE;
+}
+
+/**
+ * Check if a file should be served from the CDN.
+ *
+ * @param $path
+ *   Path to a file; relative to the Drupal root directory.
+ */
+function cdn_check_file($path) {
+  $file_path_blacklist = variable_get(CDN_EXCEPTION_FILE_PATH_BLACKLIST_VARIABLE, CDN_EXCEPTION_FILE_PATH_BLACKLIST_DEFAULT);
+  $file_path_whitelist = variable_get(CDN_EXCEPTION_FILE_PATH_WHITELIST_VARIABLE, CDN_EXCEPTION_FILE_PATH_WHITELIST_DEFAULT);
+  $module_blacklist    = cdn_get_blacklist();
+
+  // A file should not be served from a CDN when it matches one of the
+  // blacklists, except when it matches the whitelist.
+  if ((
+        drupal_match_path($path, $file_path_blacklist)
+        ||
+        drupal_match_path($path, $module_blacklist)
+      )
+      && !drupal_match_path($path, $file_path_whitelist)
+    )
+  {
+      return FALSE;
+  }
+
+  return TRUE;
+}
+
+/**
  * Helper function to efficiently load include files for this module.
  */
 function cdn_load_include($basename) {