diff --git a/mail-notify.gemspec b/mail-notify.gemspec
index 319c586..c4d0f2b 100644
--- a/mail-notify.gemspec
+++ b/mail-notify.gemspec
@@ -35,7 +35,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "standard", "~> 1"
   spec.add_development_dependency "sqlite3", "~> 1.6.2"
   spec.add_development_dependency "webmock", "~> 3.16.0"
-  spec.add_development_dependency "rspec-mocks", "~> 3.12.6"
+  spec.add_development_dependency "rspec-mocks", "~> 3.13.0"
 
   spec.add_dependency "actionmailer", ">= 5.2.4.6"
   spec.add_dependency "activesupport", ">= 5.2.4.6"