diff --git a/Gemfile b/Gemfile
index e1424ee60e4c1e3b61c77d2f28e28505d90e14f7..85bb83925d2ee739a4d4c1f0769103de4cfc7da9 100644
--- a/Gemfile
+++ b/Gemfile
@@ -34,7 +34,7 @@ group(:development) do
 end
 
 group(:test) do
-	gem "minitest"
+	gem "minitest", "<= 5.15.0"
 	gem "rack-test"
 	gem "rake"
 	gem "rantly"