diff --git a/Gemfile.lock b/Gemfile.lock
index 2bf8307..5399812 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -46,7 +46,7 @@ GEM
     psych (2.2.4)
     rack (2.0.3)
     rake (12.3.0)
-    rdoc (6.0.1)
+    rdoc (6.3.1)
     rspec (3.7.0)
       rspec-core (~> 3.7.0)
       rspec-expectations (~> 3.7.0)