diff --git a/Gemfile.lock b/Gemfile.lock
index 28d56c0..ed09f77 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -76,6 +76,10 @@ GEM
     nio4r (2.5.8)
     nokogiri (1.13.3-x86_64-darwin)
       racc (~> 1.4)
+    nokogiri (1.13.3-x86_64-linux)
+      racc (~> 1.4)
+    psych (4.0.3)
+      stringio
     racc (1.6.0)
     rack (2.2.3)
     rack-test (1.1.0)
@@ -105,7 +109,8 @@ GEM
       rake (>= 0.8.7)
       thor (>= 0.19.0, < 2.0)
     rake (13.0.6)
-    rdoc (5.1.0)
+    rdoc (6.4.0)
+      psych (>= 4.0.0)
     sprockets (4.0.2)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
@@ -113,6 +118,7 @@ GEM
       actionpack (>= 5.2)
       activesupport (>= 5.2)
       sprockets (>= 3.0.0)
+    stringio (3.0.1)
     thor (1.2.1)
     thread_safe (0.3.6)
     tzinfo (1.2.9)
@@ -123,12 +129,13 @@ GEM
 
 PLATFORMS
   x86_64-darwin-19
+  x86_64-linux
 
 DEPENDENCIES
   openlab_ruby!
   rails (~> 5)
   rake
-  rdoc (~> 5)
+  rdoc (~> 6)
 
 BUNDLED WITH
    2.3.8
diff --git a/openlab_ruby.gemspec b/openlab_ruby.gemspec
index 4b25da0..755e334 100644
--- a/openlab_ruby.gemspec
+++ b/openlab_ruby.gemspec
@@ -19,6 +19,6 @@ Gem::Specification.new do |s|
 
   s.add_dependency "httparty", "~> 0.20"
   s.add_development_dependency "rails", "~> 5"
-  s.add_development_dependency "rdoc", "~> 5"
+  s.add_development_dependency "rdoc", "~> 6"
   s.add_development_dependency "rake"
 end