diff --git a/lib/puma/cluster.rb b/lib/puma/cluster.rb
index 7bd3cc4cdb..d4c1957825 100644
--- a/lib/puma/cluster.rb
+++ b/lib/puma/cluster.rb
@@ -229,8 +229,8 @@ def wakeup!
     end
 
     def worker(index, master)
-      title = "puma: cluster worker #{index}: #{master}"
-      title << " [#{@options[:tag]}]" if @options[:tag] && !@options[:tag].empty?
+      title  = "puma: cluster worker #{index}: #{master}"
+      title += " [#{@options[:tag]}]" if @options[:tag] && !@options[:tag].empty?
       $0 = title
 
       Signal.trap "SIGINT", "IGNORE"
diff --git a/lib/puma/configuration.rb b/lib/puma/configuration.rb
index 47f9401e44..1aea28bb67 100644
--- a/lib/puma/configuration.rb
+++ b/lib/puma/configuration.rb
@@ -341,7 +341,7 @@ def self.random_token
       end
 
       if bytes
-        token = ""
+        token = "".dup
         bytes.each_byte { |b| token << b.to_s(16) }
       else
         token = (0..count).to_a.map { rand(255).to_s(16) }.join
diff --git a/lib/puma/launcher.rb b/lib/puma/launcher.rb
index ea1c301e26..48867b2c85 100644
--- a/lib/puma/launcher.rb
+++ b/lib/puma/launcher.rb
@@ -298,8 +298,8 @@ def set_process_title
     end
 
     def title
-      buffer = "puma #{Puma::Const::VERSION} (#{@options[:binds].join(',')})"
-      buffer << " [#{@options[:tag]}]" if @options[:tag] && !@options[:tag].empty?
+      buffer  = "puma #{Puma::Const::VERSION} (#{@options[:binds].join(',')})"
+      buffer += " [#{@options[:tag]}]" if @options[:tag] && !@options[:tag].empty?
       buffer
     end
 
diff --git a/test/test_http11.rb b/test/test_http11.rb
index 3eb72fec9d..2a30047065 100644
--- a/test/test_http11.rb
+++ b/test/test_http11.rb
@@ -166,8 +166,8 @@ def test_horrible_queries
     end
 
     # then large headers are rejected too
-    get = "GET /#{rand_data(10,120)} HTTP/1.1\r\n"
-    get << "X-Test: test\r\n" * (80 * 1024)
+    get  = "GET /#{rand_data(10,120)} HTTP/1.1\r\n"
+    get += "X-Test: test\r\n" * (80 * 1024)
     assert_raises Puma::HttpParserError do
       parser.execute({}, get, 0)
       parser.reset
diff --git a/test/test_persistent.rb b/test/test_persistent.rb
index 42e35b0ad9..94d7cc19a6 100644
--- a/test/test_persistent.rb
+++ b/test/test_persistent.rb
@@ -37,7 +37,7 @@ def teardown
   end
 
   def lines(count, s=@client)
-    str = ""
+    str = "".dup
     Timeout.timeout(5) do
       count.times { str << s.gets }
     end
@@ -192,7 +192,7 @@ def test_two_requests_in_one_chunk
     @server.persistent_timeout = 3
 
     req = @valid_request.to_s
-    req << "GET /second HTTP/1.1\r\nHost: test.com\r\nContent-Type: text/plain\r\n\r\n"
+    req += "GET /second HTTP/1.1\r\nHost: test.com\r\nContent-Type: text/plain\r\n\r\n"
 
     @client << req
 
@@ -209,7 +209,7 @@ def test_second_request_not_in_first_req_body
     @server.persistent_timeout = 3
 
     req = @valid_request.to_s
-    req << "GET /second HTTP/1.1\r\nHost: test.com\r\nContent-Type: text/plain\r\n\r\n"
+    req += "GET /second HTTP/1.1\r\nHost: test.com\r\nContent-Type: text/plain\r\n\r\n"
 
     @client << req