diff --git a/Gemfile.lock b/Gemfile.lock
index a1450f9..754d6a8 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -4,6 +4,7 @@ GEM
     addressable (2.8.0)
       public_suffix (>= 2.0.2, < 5.0)
     colorator (1.1.0)
+    concurrent-ruby (1.1.10)
     ffi (1.9.18)
     ffi (1.9.18-x64-mingw32)
     forwardable-extended (2.6.0)
@@ -48,9 +49,8 @@ GEM
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
-    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)
     wdm (0.1.1)