diff --git a/src/Composer/Util/Filesystem.php b/src/Composer/Util/Filesystem.php
index 2ac6a54fe..899e342cd 100644
--- a/src/Composer/Util/Filesystem.php
+++ b/src/Composer/Util/Filesystem.php
@@ -477,7 +477,7 @@ class Filesystem
      */
     public static function isLocalPath($path)
     {
-        return (bool) preg_match('{^(file://|/|/?[a-z]:[\\\\/]|\.\.[\\\\/]|[a-z0-9_.-]+[\\\\/])}i', $path);
+        return (bool) preg_match('{^(file://(?!//)|/(?!/)|/?[a-z]:[\\\\/]|\.\.[\\\\/]|[a-z0-9_.-]+[\\\\/])}i', $path);
     }
 
     public static function getPlatformPath($path)