diff --git a/Gemfile b/Gemfile
index 30c36e9..215ec0c 100644
--- a/Gemfile
+++ b/Gemfile
@@ -43,3 +43,8 @@ end
 if ENV['DB'] =~ /mongodb/
   gem 'mongoid', '~> 4.0.0', require: false
 end
+
+# Removed from Ruby 2.2 but needed for testing Rails 3.x.
+group :test do
+  gem 'test-unit', '~> 3.0'
+end
diff --git a/Rakefile b/Rakefile
index 9d533d6..67cbb18 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,11 +1,15 @@
 require 'bundler'
 require 'rspec/core/rake_task'
+require 'active_record'
 
 Bundler::GemHelper.install_tasks
 
 RSpec::Core::RakeTask.new(:spec) do |rspec|
   ENV['SPEC'] = 'spec/ransack/**/*_spec.rb'
-  rspec.rspec_opts = ['--backtrace']
+  if ActiveRecord::VERSION::MAJOR >= 4 || RUBY_VERSION < '2.2'
+    # Raises `invalid option: --backtrace` with Rails 3.x on Ruby 2.2
+    rspec.rspec_opts = ['--backtrace']
+  end
 end
 
 RSpec::Core::RakeTask.new(:mongoid) do |rspec|
diff --git a/spec/ransack/dependencies_spec.rb b/spec/ransack/dependencies_spec.rb
index ca669b9..4cb7261 100644
--- a/spec/ransack/dependencies_spec.rb
+++ b/spec/ransack/dependencies_spec.rb
@@ -1,8 +1,12 @@
-unless ::ActiveRecord::VERSION::STRING >= '4'
+ruby, rails  = RUBY_VERSION, ::ActiveRecord::VERSION::STRING.first(3)
+
+if %w(3.2 4.0 4.1).include?(rails) || (%w(3.0 3.1).include?(rails) && ruby < '2.2')
+
   describe 'Ransack' do
     it 'can be required without errors' do
       output = `bundle exec ruby -e "require 'ransack'" 2>&1`
       expect(output).to be_empty
     end
   end
+
 end