doesn't modify params in SafeBuffer#%

activesupport/lib/active_support/core_ext/string/output_safety.rb

@@ -151,9 +151,7 @@ def +(other)
     end
 
     def %(args)
-      args = Array(args)
-
-      args.map! do |arg|
+      args = Array(args).map do |arg|
         if !html_safe? || arg.html_safe?
           arg
         else

activesupport/test/core_ext/string_ext_test.rb

@@ -463,6 +463,13 @@ def to_s
     assert @other_string.html_safe?
   end
 
+  test "Concatting with % doesn't modify a string" do
+    @other_string = ["<p>", "<b>", "<h1>"]
+    "%s %s %s".html_safe % @other_string
+
+    assert_equal ["<p>", "<b>", "<h1>"], @other_string
+  end
+
   test "Concatting a fixnum to safe always yields safe" do
     string = @string.html_safe
     string = string.concat(13)