diff --git a/includes/common.inc b/includes/common.inc
index 633ab0f7422..f62b35d3c67 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -2074,7 +2074,7 @@ function _drupal_load_stylesheet($matches) {
  * Delete all cached CSS files.
  */
 function drupal_clear_css_cache() {
-  file_scan_directory(file_create_path('css'), '/.*/', array('.', '..', 'CVS'), 'file_unmanaged_delete', TRUE);
+  file_scan_directory(file_create_path('css'), '/.*/', '/(\.\.?|CVS)$/', 'file_unmanaged_delete', TRUE);
 }
 
 /**
@@ -2484,7 +2484,7 @@ function drupal_build_js_cache($files, $filename) {
  * Delete all cached JS files.
  */
 function drupal_clear_js_cache() {
-  file_scan_directory(file_create_path('js'), '/.*/', array('.', '..', 'CVS'), 'file_unmanaged_delete', TRUE);
+  file_scan_directory(file_create_path('js'), '/.*/', '/(\.\.?|CVS)$/', 'file_unmanaged_delete', TRUE);
   variable_set('javascript_parsed', array());
 }
 
@@ -2855,7 +2855,7 @@ function drupal_system_listing($mask, $directory, $key = 'name', $min_depth = 1)
 
   // Get current list of items
   foreach ($searchdir as $dir) {
-    $files = array_merge($files, file_scan_directory($dir, $mask, array('.', '..', 'CVS'), 0, TRUE, $key, $min_depth));
+    $files = array_merge($files, file_scan_directory($dir, $mask, '/(\.\.?|CVS)$/', 0, TRUE, $key, $min_depth));
   }
 
   return $files;
diff --git a/includes/file.inc b/includes/file.inc
index b79525b5bcc..d79b9bd2c8c 100644
--- a/includes/file.inc
+++ b/includes/file.inc
@@ -1259,7 +1259,7 @@ function file_download() {
  * @param $mask
  *   The preg_match() regular expression of the files to find.
  * @param $nomask
- *   An array of files/directories to ignore.
+ *   The preg_match() regular expression of the files to ignore.
  * @param $callback
  *   The callback function to call for each match.
  * @param $recurse
@@ -1280,13 +1280,13 @@ function file_download() {
  *   "path", "basename", and "name" members corresponding to the
  *   matching files.
  */
-function file_scan_directory($dir, $mask, $nomask = array('.', '..', 'CVS'), $callback = 0, $recurse = TRUE, $key = 'filename', $min_depth = 0, $depth = 0) {
+function file_scan_directory($dir, $mask, $nomask = '/(\.\.?|CVS)$/', $callback = 0, $recurse = TRUE, $key = 'filename', $min_depth = 0, $depth = 0) {
   $key = (in_array($key, array('filename', 'basename', 'name')) ? $key : 'filename');
   $files = array();
 
   if (is_dir($dir) && $handle = opendir($dir)) {
     while (FALSE !== ($file = readdir($handle))) {
-      if (!in_array($file, $nomask) && $file[0] != '.') {
+      if (!preg_match($nomask, $file) && $file[0] != '.') {
         if (is_dir("$dir/$file") && $recurse) {
           // Give priority to files in this folder by merging them in after any subdirectory files.
           $files = array_merge(file_scan_directory("$dir/$file", $mask, $nomask, $callback, $recurse, $key, $min_depth, $depth + 1), $files);
diff --git a/includes/locale.inc b/includes/locale.inc
index 00db655f7f9..9eded673783 100644
--- a/includes/locale.inc
+++ b/includes/locale.inc
@@ -97,7 +97,7 @@ function theme_locale_languages_overview_form($form) {
   $header = array(array('data' => t('English name')), array('data' => t('Native name')), array('data' => t('Code')), array('data' => t('Direction')), array('data' => t('Enabled')), array('data' => t('Default')), array('data' => t('Weight')), array('data' => t('Operations')));
   $output = theme('table', $header, $rows, array('id' => 'language-order'));
   $output .= drupal_render($form);
-  
+
   drupal_add_tabledrag('language-order', 'order', 'sibling', 'language-order-weight');
 
   return $output;
@@ -2485,7 +2485,7 @@ function locale_batch_by_language($langcode, $finished = NULL, $skip = array())
     // with names ending with $langcode.po. This allows for filenames
     // like node-module.de.po to let translators use small files and
     // be able to import in smaller chunks.
-    $files = array_merge($files, file_scan_directory(dirname($component->filename) . '/translations', '/(^|\.)' . $langcode . '\.po$/', array('.', '..', 'CVS'), 0, FALSE));
+    $files = array_merge($files, file_scan_directory(dirname($component->filename) . '/translations', '/(^|\.)' . $langcode . '\.po$/', '/(\.\.?|CVS)$/', 0, FALSE));
     $components[] = $component->name;
   }
 
@@ -2517,7 +2517,7 @@ function locale_batch_by_component($components, $finished = '_locale_batch_syste
         // as $langcode.po or with names ending with $langcode.po. This allows
         // for filenames like node-module.de.po to let translators use small
         // files and be able to import in smaller chunks.
-        $files = array_merge($files, file_scan_directory(dirname($component->filename) . '/translations', '/(^|\.)(' . $language_list . ')\.po$/', array('.', '..', 'CVS'), 0, FALSE));
+        $files = array_merge($files, file_scan_directory(dirname($component->filename) . '/translations', '/(^|\.)(' . $language_list . ')\.po$/', '/(\.\.?|CVS)$/', 0, FALSE));
       }
     }
     return _locale_batch_build($files, $finished);
diff --git a/install.php b/install.php
index caa5feb3ea0..4a5df926f5d 100644
--- a/install.php
+++ b/install.php
@@ -410,7 +410,7 @@ function install_settings_form_submit($form, &$form_state) {
  * Find all .profile files.
  */
 function install_find_profiles() {
-  return file_scan_directory('./profiles', '/\.profile$/', array('.', '..', 'CVS'), 0, TRUE, 'name', 0);
+  return file_scan_directory('./profiles', '/\.profile$/', '/(\.\.?|CVS)$/', 0, TRUE, 'name', 0);
 }
 
 /**
@@ -496,7 +496,7 @@ function install_select_profile_form(&$form_state, $profile_files) {
  * Find all .po files for the current profile.
  */
 function install_find_locales($profilename) {
-  $locales = file_scan_directory('./profiles/' . $profilename . '/translations', '/\.po$/', array('.', '..', 'CVS'), 0, FALSE);
+  $locales = file_scan_directory('./profiles/' . $profilename . '/translations', '/\.po$/', '/(\.\.?|CVS)$/', 0, FALSE);
   array_unshift($locales, (object) array('name' => 'en'));
   return $locales;
 }
diff --git a/modules/simpletest/tests/file.test b/modules/simpletest/tests/file.test
index 564ecea3503..e383defcaee 100644
--- a/modules/simpletest/tests/file.test
+++ b/modules/simpletest/tests/file.test
@@ -541,6 +541,38 @@ class FileDirectoryTest extends FileTestCase {
 }
 
 
+/**
+ * Tests the file_scan_directory() function.
+ */
+class FileScanDirectoryTest extends FileTestCase {
+  /**
+   * Implementation of getInfo().
+   */
+  function getInfo() {
+    return array(
+      'name' => t('File scan directory'),
+      'description' => t('Tests the file_scan_directory() function.'),
+      'group' => t('File'),
+    );
+  }
+
+  /**
+   * Check that the no-mask parameter is honored.
+   */
+  function testNoMask() {
+    $path = $this->original_file_directory . '/simpletest';
+
+    // Grab a listing of all the JS files.
+    $all_files = file_scan_directory($path, '/javascript*/');
+    $this->assertEqual(2, count($all_files), t('Found two, expected javascript files.'));
+
+    // Now use the nomask parameter to filter out the .script file.
+    $filtered_files = file_scan_directory($path, '/javascript*/', '/.script$/');
+    $this->assertEqual(1, count($filtered_files), t('Filtered correctly.'));
+  }
+}
+
+
 /**
  * Deletion related tests.
  */