diff --git a/.travis.yml b/.travis.yml
index 438d89596..dcfd6e5c9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,6 +7,7 @@ rvm:
   - 2.1
   - 2.2
   - 2.3.0
+  - 2.4.1
   - jruby-18mode
   - jruby-19mode
   - jruby-9.0.5.0
@@ -16,6 +17,9 @@ gemfile: ".travis/Gemfile"
 
 sudo: false
 
+before_script:
+- if (ruby -e "exit RUBY_VERSION.to_f >= 2.4"); then export RUBYOPT="--enable-frozen-string-literal"; fi; echo $RUBYOPT
+
 env:
   global:
     - VERBOSE=true
diff --git a/.travis/Gemfile b/.travis/Gemfile
index 3fd116321..9e4a237cf 100644
--- a/.travis/Gemfile
+++ b/.travis/Gemfile
@@ -9,3 +9,9 @@ when "synchrony"
   gem "hiredis"
   gem "em-synchrony"
 end
+
+if RUBY_VERSION.to_f < 1.9
+  gem 'test-unit', '3.1.5'
+else
+  gem 'test-unit', '>= 3.2.5'
+end
diff --git a/Gemfile b/Gemfile
index 73d38bc2e..b14f14cdd 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,3 +2,9 @@
 source 'https://rubygems.org'
 
 gemspec
+
+if RUBY_VERSION.to_f < 1.9
+  gem 'test-unit', '3.1.5'
+else
+  gem 'test-unit', '>= 3.2.5'
+end
diff --git a/lib/redis.rb b/lib/redis.rb
index c61d4838e..b83407748 100644
--- a/lib/redis.rb
+++ b/lib/redis.rb
@@ -44,6 +44,7 @@ def self.current=(redis)
   # @option options [Boolean] :inherit_socket (false) Whether to use socket in forked process or not
   # @option options [Array] :sentinels List of sentinels to contact
   # @option options [Symbol] :role (:master) Role to fetch via Sentinel, either `:master` or `:slave`
+  # @option options [String] :master_name Master group name according to the `monitor` line in Sentinel config
   #
   # @return [Redis] a new client instance
   def initialize(options = {})
diff --git a/lib/redis/client.rb b/lib/redis/client.rb
index 31be2de33..67aca78cc 100644
--- a/lib/redis/client.rb
+++ b/lib/redis/client.rb
@@ -509,7 +509,7 @@ def initialize(options)
 
           @sentinels = @options.delete(:sentinels).dup
           @role = @options.fetch(:role, "master").to_s
-          @master = @options[:host]
+          @master = @options[:master_name] || @options[:host]
         end
 
         def check(client)
diff --git a/lib/redis/connection/ruby.rb b/lib/redis/connection/ruby.rb
index 96f1d6a59..c01edd913 100644
--- a/lib/redis/connection/ruby.rb
+++ b/lib/redis/connection/ruby.rb
@@ -39,7 +39,7 @@ def initialize(*args)
         super(*args)
 
         @timeout = @write_timeout = nil
-        @buffer = ""
+        @buffer = "".dup
       end
 
       def timeout=(timeout)
diff --git a/redis.gemspec b/redis.gemspec
index 3099b6d9b..a661410dd 100644
--- a/redis.gemspec
+++ b/redis.gemspec
@@ -40,5 +40,5 @@ Gem::Specification.new do |s|
   s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
 
   s.add_development_dependency("rake", "<11.0.0")
-  s.add_development_dependency("test-unit", "3.1.5")
+  s.add_development_dependency("test-unit", ">= 3.1.5")
 end
diff --git a/test/sentinel_test.rb b/test/sentinel_test.rb
index 823e0762c..7e9b4e005 100644
--- a/test/sentinel_test.rb
+++ b/test/sentinel_test.rb
@@ -196,6 +196,32 @@ def test_sentinel_role_mismatch
     assert_match(/Instance role mismatch/, ex.message)
   end
 
+  def test_sentinel_master_name
+    sentinels = [{:host => "127.0.0.1", :port => 26381}]
+
+    commands = {
+      :s1 => [],
+    }
+
+    handler = lambda do |id|
+      {
+        :sentinel => lambda do |command, *args|
+          commands[id] << [command, *args]
+          ["127.0.0.1", "6381"]
+        end
+      }
+    end
+
+    RedisMock.start(handler.call(:s1)) do |s1_port|
+      sentinels[0][:port] = s1_port
+      redis = Redis.new(:url => "redis://master1", :sentinels => sentinels, :role => :master, :master_name => :new_master)
+
+      assert redis.ping
+    end
+
+    assert_equal commands[:s1], [%w[get-master-addr-by-name new_master]]
+  end
+
   def test_sentinel_retries
     sentinels = [{:host => "127.0.0.1", :port => 26381},
                  {:host => "127.0.0.1", :port => 26382}]