diff --git a/Gemfile b/Gemfile
index 8fcb1c3..fb08ebd 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,5 +5,5 @@ gem "test-unit"
 
 group :sig do
   gem "rbs"
-  gem "rdoc", "<= 6.11"
+  gem "rdoc"
 end
diff --git a/Rakefile b/Rakefile
index ac434b2..a533fe1 100644
--- a/Rakefile
+++ b/Rakefile
@@ -17,8 +17,8 @@ namespace :rbs do
     require "pathname"
 
     Dir.mktmpdir do |tmpdir|
-      system("rdoc --ri --output #{tmpdir}/doc --root=. lib")
-      system("rbs annotate --no-system --no-gems --no-site --no-home -d #{tmpdir}/doc sig")
+      sh("rdoc --ri --output #{tmpdir}/doc --root=. lib")
+      sh("rbs annotate --no-system --no-gems --no-site --no-home -d #{tmpdir}/doc sig")
     end
   end