3 files changed, 5 insertions, 5 deletions
diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index 3c91677d55..4155c155da 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -103,7 +103,7 @@ module ActionDispatch # :nodoc:
 
       def body
         @str_body ||= begin
-          buf = ""
+          buf = "".dup
           each { |chunk| buf << chunk }
           buf
         end
diff --git a/actionpack/lib/action_dispatch/journey/router/utils.rb b/actionpack/lib/action_dispatch/journey/router/utils.rb
index 6d400f3364..1ac86d10d6 100644
--- a/actionpack/lib/action_dispatch/journey/router/utils.rb
+++ b/actionpack/lib/action_dispatch/journey/router/utils.rb
@@ -14,11 +14,11 @@ module ActionDispatch
         #   normalize_path("/%ab")  # => "/%AB"
         def self.normalize_path(path)
           encoding = path.encoding
-          path = "/#{path}"
+          path = "/#{path}".dup
           path.squeeze!("/".freeze)
           path.sub!(%r{/+\Z}, "".freeze)
           path.gsub!(/(%[a-f0-9]{2})/) { $1.upcase }
-          path = "/" if path == "".freeze
+          path = "/".dup if path == "".freeze
           path.force_encoding(encoding)
           path
         end
@@ -29,7 +29,7 @@ module ActionDispatch
           ENCODE   = "%%%02X".freeze
           US_ASCII = Encoding::US_ASCII
           UTF_8    = Encoding::UTF_8
-          EMPTY    = "".force_encoding(US_ASCII).freeze
+          EMPTY    = "".dup.force_encoding(US_ASCII).freeze
           DEC2HEX  = (0..255).to_a.map { |i| ENCODE % i }.map { |s| s.force_encoding(US_ASCII) }
 
           ALPHA = "a-zA-Z".freeze
diff --git a/actionpack/lib/action_dispatch/testing/assertions/response.rb b/actionpack/lib/action_dispatch/testing/assertions/response.rb
index 1baf979ac9..749f2eab57 100644
--- a/actionpack/lib/action_dispatch/testing/assertions/response.rb
+++ b/actionpack/lib/action_dispatch/testing/assertions/response.rb
@@ -79,7 +79,7 @@ module ActionDispatch
         def generate_response_message(expected, actual = @response.response_code)
           "Expected response to be a <#{code_with_name(expected)}>,"\
           " but was a <#{code_with_name(actual)}>"
-            .concat(location_if_redirected).concat(response_body_if_short)
+            .dup.concat(location_if_redirected).concat(response_body_if_short)
         end
 
         def response_body_if_short