diff --git a/.travis.yml b/.travis.yml
index f79d59cfd..e5d43d917 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -40,6 +40,6 @@ matrix:
     - rvm: rbx-2
     - script: ./ci/run_rubocop_specs
 before_install:
-  - gem install bundler
+  - gem install bundler -v '< 2'
   - bundle --version
   - gem --version
diff --git a/lib/parser/tree_rewriter.rb b/lib/parser/tree_rewriter.rb
index 4b0c071d5..60ffacedb 100644
--- a/lib/parser/tree_rewriter.rb
+++ b/lib/parser/tree_rewriter.rb
@@ -27,12 +27,13 @@ module Parser
   #     end
   #     EOF
   #
+  #     ast           = Parser::CurrentRuby.parse code
   #     buffer        = Parser::Source::Buffer.new('(example)')
   #     buffer.source = code
   #     rewriter      = RemoveDo.new
   #
   #     # Rewrite the AST, returns a String with the new form.
-  #     puts rewriter.rewrite(buffer)
+  #     puts rewriter.rewrite(buffer, ast)
   #
   # This would result in the following Ruby code:
   #
diff --git a/parser.gemspec b/parser.gemspec
index 06104d4ca..603eec8c4 100644
--- a/parser.gemspec
+++ b/parser.gemspec
@@ -35,7 +35,7 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency             'ast',       '~> 2.4.0'
 
-  spec.add_development_dependency 'bundler',   '~> 1.15'
+  spec.add_development_dependency 'bundler',   '>= 1.15', '< 3.0.0'
   spec.add_development_dependency 'rake',      '~> 10.0'
   spec.add_development_dependency 'racc',      '= 1.4.14'
   spec.add_development_dependency 'cliver',    '~> 0.3.2'