diff --git a/Gemfile b/Gemfile
index 7c990eb..b0581c0 100644
--- a/Gemfile
+++ b/Gemfile
@@ -19,7 +19,7 @@ group :test do
   gem 'rack', '>= 2.0.6', :platforms => %i[jruby_18 jruby_19 ruby_19 ruby_20 ruby_21]
   gem 'rack-test'
   gem 'rest-client', '~> 2.0.0', :platforms => [:jruby_18]
-  gem 'rspec', '~> 3.5.0'
+  gem 'rspec', '~> 3.5'
   gem 'rubocop', '>= 0.58.2', '< 0.69.0', :platforms => %i[ruby_20 ruby_21 ruby_22 ruby_23 ruby_24]
   gem 'simplecov-lcov'
   gem 'tins', '~> 1.13', :platforms => %i[jruby_18 jruby_19 ruby_19]
diff --git a/spec/omniauth/form_spec.rb b/spec/omniauth/form_spec.rb
index 1b9c88c..1354a16 100644
--- a/spec/omniauth/form_spec.rb
+++ b/spec/omniauth/form_spec.rb
@@ -33,7 +33,7 @@ describe OmniAuth::Form do
 
   describe '#html' do
     it 'appends to the html body' do
-      form = OmniAuth::Form.build { @html = '<p></p>' }
+      form = OmniAuth::Form.build { @html = +'<p></p>' }
       form.html('<h1></h1>')
 
       expect(form.instance_variable_get(:@html)).to eq '<p></p><h1></h1>'