diff --git a/tool/bundler/test_gems.rb b/tool/bundler/test_gems.rb
index bb7d4edb9a..2bf3a2ad65 100644
--- a/tool/bundler/test_gems.rb
+++ b/tool/bundler/test_gems.rb
@@ -8,7 +8,7 @@ gem "base64"
 gem "webrick", "~> 1.8"
 gem "rack-test", "~> 2.1"
 gem "compact_index", "~> 0.15.0"
-gem "sinatra", "~> 4.0"
+gem "sinatra", "< 4.1"
 gem "rake", "~> 13.1"
 gem "builder", "~> 3.2"
 gem "rb_sys"