diff --git a/test/test_helper.rb b/test/test_helper.rb
index af319fd..3252b05 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -1,3 +1,8 @@
+require 'simplecov'
+SimpleCov.start do
+  add_filter "/test/"
+end
+
 require 'minitest/autorun'
 require 'minitest/spec'
 
diff --git a/threadlocal.gemspec b/threadlocal.gemspec
index 771b166..83abccd 100644
--- a/threadlocal.gemspec
+++ b/threadlocal.gemspec
@@ -17,4 +17,5 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "bundler", "~> 1.5"
   spec.add_development_dependency "rake"
+  spec.add_development_dependency "simplecov", "~> 0.7.1" # see https://github.com/colszowka/simplecov/issues/281
 end