diff --git a/review/coder/pifr_coder.client.inc b/review/coder/pifr_coder.client.inc
index f083477..8773dfa 100644
--- a/review/coder/pifr_coder.client.inc
+++ b/review/coder/pifr_coder.client.inc
@@ -79,6 +79,7 @@ class pifr_client_review_pifr_coder extends pifr_client_review_pifr_drupal {
     $status['total'] = count($files);
 
     $not_found = 0;
+    $ignored = 0;
     foreach ($files as $file) {
       // Update variable status to keep status() up-to-date.
       $status['position']++;
@@ -93,6 +94,16 @@ class pifr_client_review_pifr_coder extends pifr_client_review_pifr_drupal {
         continue;
       }
 
+      // If reviewing Drupal Core, exclude any external files from the review
+      if ($this->test['vcs']['main']['repository']['url'] == $this->core_url) {
+        foreach ($this->coder_core_ignore_list() as $ignore) {
+          if (substr($file, 0, $ignore['length']) == $ignore['fileprefix']) {
+            $ignored++;
+            continue 2;
+          }
+        }
+      }
+
       $args['#filename'] = $filepath;
       $this->results[$file] = do_coder_reviews($args);
 
@@ -102,9 +113,27 @@ class pifr_client_review_pifr_coder extends pifr_client_review_pifr_drupal {
       }
     }
 
-    $this->log('Reviewed [' . (count($files) - $not_found) . ' of ' . count($files) . '] relevant file(s).');
+    $this->log('Reviewed [' . (count($files) - $ignored - $not_found) . ' of ' . count($files) - $ignored . '] relevant file(s).');
+  }
+
+  /**
+   * Get a list of files that should be ignored by coder.
+   *
+   * Each item in the returned array should be an array of the form
+   * array('file' => 'file_or_directory_prefix_to_match',
+   *       'length' => 'length of file or directory prefix to match')
+   *
+   * @return array List of core files that should be ignored by coder.
+   */
+  protected function coder_core_ignore_list() {
+    return array(
+      array('file' => 'core/includes/Symfony', 'length' => 21),
+      array('file' => 'core/misc/jquery', 'length' => 16),
+      array('file' => 'core/modules/system/system.tar.inc', 'length' => 34),
+    );
   }
 
+
   /**
    * Get a list of files that should be reviewed by coder.
    *