diff --git a/Gemfile.lock b/Gemfile.lock
index edb5f47..f3e850a 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -4,6 +4,7 @@ GEM
     addressable (2.5.1)
       public_suffix (~> 2.0, >= 2.0.2)
     colorator (1.1.0)
+    concurrent-ruby (1.1.10)
     ffi (1.9.18)
     ffi (1.9.18-x64-mingw32)
     forwardable-extended (2.6.0)
@@ -37,9 +38,8 @@ GEM
     rouge (1.11.1)
     safe_yaml (1.0.4)
     sass (3.4.23)
-    thread_safe (0.3.6)
-    tzinfo (1.2.3)
-      thread_safe (~> 0.1)
+    tzinfo (2.0.5)
+      concurrent-ruby (~> 1.0)
     tzinfo-data (1.2017.2)
       tzinfo (>= 1.0.0)