diff --git a/Gemfile b/Gemfile
index 5b53bab..8598ec6 100644
--- a/Gemfile
+++ b/Gemfile
@@ -12,6 +12,6 @@ group :development, :test do
 end
 
 group :example do
-  gem 'sinatra'
+  gem 'sinatra', '>= 4.0.0'
   gem 'thin'
 end