Gemfile in rbs-2.8.4 vs Gemfile in rbs-3.0.0.dev.1

@@ -16,10 +16,10 @@
 gem "goodcheck"
 gem "dbm"
 gem 'digest'
 gem 'tempfile'
 gem "prime"
-gem "rdoc"
+gem "rdoc", "< 6.5.0"
 
 # Test gems
 gem "rbs-amber", path: "test/assets/test-gem"
 
 group :ide, optional: true do