diff --git a/2021/ruby/Gemfile.lock b/2021/ruby/Gemfile.lock
index 29ef029..159ebc5 100644
--- a/2021/ruby/Gemfile.lock
+++ b/2021/ruby/Gemfile.lock
@@ -14,7 +14,7 @@ GEM
       method_source (~> 0.9.0)
     rainbow (3.0.0)
     regexp_parser (2.1.1)
-    rexml (3.2.5)
+    rexml (3.3.9)
     rspec (3.8.0)
       rspec-core (~> 3.8.0)
       rspec-expectations (~> 3.8.0)