diff --git a/src/Composer/Autoload/ClassLoader.php b/src/Composer/Autoload/ClassLoader.php
index 38de12c72..a4a0dc5a6 100644
--- a/src/Composer/Autoload/ClassLoader.php
+++ b/src/Composer/Autoload/ClassLoader.php
@@ -202,6 +202,6 @@ class ClassLoader
             return $file;
         }
 
-        $this->classMap[$class] = false;
+        return $this->classMap[$class] = false;
     }
 }