diff --git a/steep/Gemfile.lock b/steep/Gemfile.lock
index 633a722c1..9f3d7ab01 100644
--- a/steep/Gemfile.lock
+++ b/steep/Gemfile.lock
@@ -18,7 +18,7 @@ GEM
     base64 (0.2.0)
     benchmark (0.4.0)
     bigdecimal (3.1.9)
-    concurrent-ruby (1.3.4)
+    concurrent-ruby (1.3.5)
     connection_pool (2.5.0)
     csv (3.3.2)
     drb (2.2.1)