diff --git a/.circleci/gemspec_compatible b/.circleci/gemspec_compatible
index 4481b12..7c4bac4 100644
--- a/.circleci/gemspec_compatible
+++ b/.circleci/gemspec_compatible
@@ -40,7 +40,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'pry-byebug', '~> 3.9'
   spec.add_development_dependency 'rake', '~> 13.0', '>= 13.0.6'
   spec.add_development_dependency 'rspec', '~> 3.10'
-  spec.add_development_dependency 'simplecov', '~> 0.17.1'
   spec.add_development_dependency 'smtp_mock', '~> 0.1.1'
   spec.add_development_dependency 'truemail-rspec', '~> 0.7.0'
   spec.add_development_dependency 'webmock', '~> 3.14'
diff --git a/truemail.gemspec b/truemail.gemspec
index 71cf99c..e737e88 100644
--- a/truemail.gemspec
+++ b/truemail.gemspec
@@ -47,7 +47,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rubocop', '~> 1.24', '>= 1.24.1'
   spec.add_development_dependency 'rubocop-performance', '~> 1.13', '>= 1.13.2'
   spec.add_development_dependency 'rubocop-rspec', '~> 2.7'
-  spec.add_development_dependency 'simplecov', '~> 0.17.1'
+  spec.add_development_dependency 'simplecov', '~> 0.21.2'
   spec.add_development_dependency 'smtp_mock', '~> 0.1.1'
   spec.add_development_dependency 'truemail-rspec', '~> 0.7.0'
   spec.add_development_dependency 'webmock', '~> 3.14'