diff --git a/src/RuleSet/Loader/ComposerLoader.php b/src/RuleSet/Loader/ComposerLoader.php
index 652f5c8..81c3948 100644
--- a/src/RuleSet/Loader/ComposerLoader.php
+++ b/src/RuleSet/Loader/ComposerLoader.php
@@ -119,16 +119,16 @@ private function getComposerPackages(\stdClass $composer, $noDev = false)
     /**
      * @param $package
      *
-     * @return RuleSet
+     * @return RuleSet|null
      */
     private function loadPackageRuleSet(\stdClass $package)
     {
-        $key = $this->generatePackageKey($package);
+        $ruleSet = null;
+        $key     = $this->generatePackageKey($package);
 
         if ($this->cache->has($key)) {
             $ruleSet = $this->cache->getCachedRuleSet($key);
-        } else {
-            $path = $this->getPackagePath($package);
+        } elseif (is_dir($path = $this->getPackagePath($package))) {
             $ruleSet = $this->traverser->traverse($path, true);
             $this->cache->cacheRuleSet($key, $ruleSet);
         }