diff --git a/Gemfile.lock b/Gemfile.lock
index e663bfd..1c540e6 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -4,6 +4,7 @@ GEM
     addressable (2.5.2)
       public_suffix (>= 2.0.2, < 4.0)
     colorator (1.1.0)
+    concurrent-ruby (1.1.10)
     ffi (1.9.25)
     ffi (1.9.25-x64-mingw32)
     forwardable-extended (2.6.0)
@@ -51,9 +52,8 @@ 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 (1.2.5)
-      thread_safe (~> 0.1)
+    tzinfo (2.0.5)
+      concurrent-ruby (~> 1.0)
     tzinfo-data (1.2018.5)
       tzinfo (>= 1.0.0)