Gemfile in appmap-0.88.0 vs Gemfile in appmap-0.89.0

@@ -1,5 +1,7 @@
 source "https://rubygems.org"
 
 git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
 
 gemspec
+
+gem 'rack', '~> 2'