diff --git a/Gemfile.lock b/Gemfile.lock
index 37488dd..0de0881 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -8,7 +8,7 @@ GEM
       babel-source (>= 4.0, < 6)
       execjs (~> 2.0)
     colorator (1.1.0)
-    concurrent-ruby (1.1.6)
+    concurrent-ruby (1.3.7)
     cssminify2 (2.0.1)
     em-websocket (0.5.1)
       eventmachine (>= 0.12.9)