diff --git a/active_model_otp.gemspec b/active_model_otp.gemspec
index 66fc920..3a7a9b0 100644
--- a/active_model_otp.gemspec
+++ b/active_model_otp.gemspec
@@ -25,7 +25,7 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "activerecord"
   spec.add_development_dependency "rake"
-  spec.add_development_dependency "minitest", "~> 5.4.2"
+  spec.add_development_dependency "minitest", "~> 5.20.0"
   spec.add_development_dependency "appraisal"
 
   if RUBY_PLATFORM == "java"