diff --git a/examples/rack/Gemfile b/examples/rack/Gemfile
index 413fe5ea..350a5d34 100644
--- a/examples/rack/Gemfile
+++ b/examples/rack/Gemfile
@@ -1,5 +1,5 @@
 source 'https://rubygems.org'
 
 gem 'prometheus-client', path: '../..'
-gem 'rack'
+gem 'rack', '< 3.0'
 gem 'unicorn'