diff --git a/lib/private/installer.php b/lib/private/installer.php
index f43969691c7bfec319000734afd79933877ed821..60ed06ae352efd02e31e91c8d1373364a1880c0d 100644
--- a/lib/private/installer.php
+++ b/lib/private/installer.php
@@ -568,7 +568,7 @@ class OC_Installer{
 
 			// iterate the bad patterns
 			foreach($blacklist as $bl) {
-				$cmd = 'grep -ri '.escapeshellarg($bl).' '.$folder.'';
+				$cmd = 'grep --include \\*.php -ri '.escapeshellarg($bl).' '.$folder.'';
 				$result = exec($cmd);
 				// bad pattern found
 				if($result<>'') {