diff --git a/Gemfile b/Gemfile
index 61c6d2785a..e6862dec9f 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,7 +5,15 @@ gemspec
 group :development do
   gem "benchmark-driver"
   gem "rake-compiler"
-  gem "rdoc"
+  if Gem::Version.new(RUBY_VERSION) < Gem::Version.new("3.2")
+    # rdoc 8 depends on rbs 4, which requires Ruby 3.2 or later.
+    gem "rdoc", "< 8"
+  else
+    gem "rdoc"
+    # rdoc 8 depends on rbs, which has no java platform gem before 4.1.0.pre.2.
+    # See https://github.com/ruby/rdoc/issues/1746
+    gem 'rbs', '>= 4.1.0.pre.2' if RUBY_PLATFORM == 'java'
+  end
   gem "ruby-maven", :platforms => :jruby
   gem "test-unit"
   gem "test-unit-ruby-core"