diff --git a/.rubocop.yml b/.rubocop.yml
index 47ed75c..1f4c59e 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,4 +1,7 @@
-require: rubocop-rspec
+require:
+  - rubocop-performance
+  - rubocop-rake
+  - rubocop-rspec
 
 AllCops:
   NewCops: enable
diff --git a/rspec-side_effects.gemspec b/rspec-side_effects.gemspec
index 0f689e0..3e776e2 100644
--- a/rspec-side_effects.gemspec
+++ b/rspec-side_effects.gemspec
@@ -36,6 +36,8 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'bundler-audit'
   spec.add_development_dependency 'license_finder'
   spec.add_development_dependency 'rubocop'
+  spec.add_development_dependency 'rubocop-performance'
+  spec.add_development_dependency 'rubocop-rake'
   spec.add_development_dependency 'rubocop-rspec'
   spec.add_development_dependency 'simplecov'
   spec.add_development_dependency 'simplecov-lcov'
diff --git a/spec/rspec/side_effects_spec.rb b/spec/rspec/side_effects_spec.rb
index 3a29d5e..5d3cde5 100644
--- a/spec/rspec/side_effects_spec.rb
+++ b/spec/rspec/side_effects_spec.rb
@@ -43,7 +43,7 @@ def test_exception
 
   # @param [#to_s] variable_name
   def expect_instance_variable(variable_name)
-    expect(test_class.instance_variable_get("@#{variable_name}"))
+    expect(test_class.instance_variable_get(:"@#{variable_name}"))
   end
 
   describe '#its_side_effects_are' do