diff --git a/dev/TestRunner.php b/dev/TestRunner.php
index 483165cfc..645a7fed5 100644
--- a/dev/TestRunner.php
+++ b/dev/TestRunner.php
@@ -52,6 +52,21 @@ class TestRunner extends Controller {
 		'$TestCase' => 'only',
 	);
 	
+	/**
+	 * @var Array Blacklist certain directories for the coverage report.
+	 * Filepaths are relative to the webroot, without leading slash.
+	 * 
+	 * @see http://www.phpunit.de/manual/current/en/appendixes.configuration.html#appendixes.configuration.blacklist-whitelist
+	 */
+	static $coverage_filter_dirs = array(
+		'cms/thirdparty',
+		'cms/tests',
+		'cms/lang',
+		'sapphire/thirdparty',
+		'sapphire/tests',
+		'sapphire/lang',
+	);
+	
 	/**
 	 * Override the default reporter with a custom configured subclass.
 	 *
@@ -264,6 +279,10 @@ class TestRunner extends Controller {
 		$results->addListener($reporter);
 
 		if($coverage === true) {
+			foreach(self::$coverage_filter_dirs as $dir) {
+				PHPUnit_Util_Filter::addDirectoryToFilter(BASE_PATH . '/' . $dir);
+			}
+			
 			$results->collectCodeCoverageInformation(true);
 			$suite->run($results);