diff --git a/rllab/mujoco_py/Gemfile.lock b/rllab/mujoco_py/Gemfile.lock
index 9847ad28..1a34e2fb 100644
--- a/rllab/mujoco_py/Gemfile.lock
+++ b/rllab/mujoco_py/Gemfile.lock
@@ -8,7 +8,9 @@ GEM
       thread_safe (~> 0.1)
       tzinfo (~> 1.1)
     coderay (1.1.0)
-    i18n (0.7.0)
+    concurrent-ruby (1.1.10)
+    i18n (0.9.5)
+      concurrent-ruby (~> 1.0)
     json (1.8.1)
     method_source (0.8.2)
     minitest (5.5.1)