3 files changed, 3 insertions, 3 deletions
diff --git a/actionpack/lib/action_controller/metal/http_authentication.rb b/actionpack/lib/action_controller/metal/http_authentication.rb
index a871ccd533..5794e0fb97 100644
--- a/actionpack/lib/action_controller/metal/http_authentication.rb
+++ b/actionpack/lib/action_controller/metal/http_authentication.rb
@@ -474,7 +474,7 @@ module ActionController
 
       # This removes the <tt>"</tt> characters wrapping the value.
       def rewrite_param_values(array_params)
-        array_params.each { |param| (param[1] || "".dup).gsub! %r/^"|"$/, "" }
+        array_params.each { |param| (param[1] || +"").gsub! %r/^"|"$/, "" }
       end
 
       # This method takes an authorization body and splits up the key-value
diff --git a/actionpack/lib/action_controller/metal/live.rb b/actionpack/lib/action_controller/metal/live.rb
index b1c2391afe..5680ef08a1 100644
--- a/actionpack/lib/action_controller/metal/live.rb
+++ b/actionpack/lib/action_controller/metal/live.rb
@@ -297,7 +297,7 @@ module ActionController
       return unless logger
 
       logger.fatal do
-        message = "\n#{exception.class} (#{exception.message}):\n".dup
+        message = +"\n#{exception.class} (#{exception.message}):\n"
         message << exception.annoted_source_code.to_s if exception.respond_to?(:annoted_source_code)
         message << "  " << exception.backtrace.join("\n  ")
         "#{message}\n\n"
diff --git a/actionpack/lib/action_controller/metal/rendering.rb b/actionpack/lib/action_controller/metal/rendering.rb
index 6d181e6456..7d0a944381 100644
--- a/actionpack/lib/action_controller/metal/rendering.rb
+++ b/actionpack/lib/action_controller/metal/rendering.rb
@@ -40,7 +40,7 @@ module ActionController
     def render_to_string(*)
       result = super
       if result.respond_to?(:each)
-        string = "".dup
+        string = +""
         result.each { |r| string << r }
         string
       else