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/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