diff --git a/app/services/ruby_releases/release_list.rb b/app/services/ruby_releases/release_list.rb
index b6bb5b335..49c68a61e 100644
--- a/app/services/ruby_releases/release_list.rb
+++ b/app/services/ruby_releases/release_list.rb
@@ -14,7 +14,7 @@ def self.fetch
 
     attr_accessor :releases
     def initialize
-      @releases = parse_index(release_index).push(dev)
+      @releases = parse_index(release_index).push(dev, ruby_3)
     end
 
     private
@@ -42,6 +42,10 @@ def dev
       RubyVersion.new("dev", sha512: "", source_url: RUBY_DEV_ZIP_URL)
     end
 
+    def ruby_3
+      RubyVersion.new("3.0-preview1", source_url: "https://cache.ruby-lang.org/pub/ruby/3.0/ruby-3.0.0-preview1.zip")
+    end
+
     def supported_release_format?(url)
       url.end_with?(SUPPORTED_RELEASE_FORMAT)
     end
diff --git a/lib/ruby_documentation_importer.rb b/lib/ruby_documentation_importer.rb
index 845a8fb75..99247bfa3 100644
--- a/lib/ruby_documentation_importer.rb
+++ b/lib/ruby_documentation_importer.rb
@@ -12,6 +12,8 @@ def self.import(release)
   end
 
   def initialize(release)
+    raise ArgumentError unless release.is_a?(RubyVersion)
+    
     @release = release
     @rdoc = RDoc::RDoc.new
     @rdoc_options = @rdoc.load_options
diff --git a/lib/ruby_downloader.rb b/lib/ruby_downloader.rb
index 42837a02e..26742dbfc 100644
--- a/lib/ruby_downloader.rb
+++ b/lib/ruby_downloader.rb
@@ -4,6 +4,7 @@ class RubyDownloader
   attr_reader :release
 
   def initialize(release)
+    raise ArgumentError unless release.is_a?(RubyVersion)
     @release = release
   end