diff --git a/src/PHPCensor/Plugin/PhpParallelLint.php b/src/PHPCensor/Plugin/PhpParallelLint.php
index 4a1cd744..831b3a4a 100644
--- a/src/PHPCensor/Plugin/PhpParallelLint.php
+++ b/src/PHPCensor/Plugin/PhpParallelLint.php
@@ -60,7 +60,7 @@ class PhpParallelLint extends Plugin
 
         if (isset($options['extensions'])) {
             // Only use if this is a comma delimited list
-            $pattern = '/^[a-z]*,\ *[a-z]*$/';
+            $pattern = '/^([a-z]+)(,\ *[a-z]*)*$/';
 
             if (preg_match($pattern, $options['extensions'])) {
                 $this->extensions = str_replace(' ', '', $options['extensions']);