diff --git a/lib/rubygems/util/atomic_file_writer.rb b/lib/rubygems/util/atomic_file_writer.rb
index be9bf76e83b8..6f75e38d51f8 100644
--- a/lib/rubygems/util/atomic_file_writer.rb
+++ b/lib/rubygems/util/atomic_file_writer.rb
@@ -53,9 +53,9 @@ def self.open(file_name)
         if old_stat
           # Set correct permissions on new file
           begin
-            File.chown(old_stat.uid, old_stat.gid, tmp_path)
+            temp_file.chown(old_stat.uid, old_stat.gid)
             # This operation will affect filesystem ACL's
-            File.chmod(old_stat.mode, tmp_path)
+            temp_file.chmod(old_stat.mode)
           rescue Errno::EPERM, Errno::EACCES
             # Changing file ownership failed, moving on.
           end
@@ -99,9 +99,7 @@ def self.open(file_name)
     # still be cut mid-character.
     def self.byteslice_at_char_boundary(string, max_bytesize)
       sliced = string.byteslice(0, max_bytesize)
-      if string.valid_encoding?
-        sliced = sliced.byteslice(0, sliced.bytesize - 1) until sliced.valid_encoding?
-      end
+      sliced.scrub!("") if string.valid_encoding?
       sliced
     end
     private_class_method :byteslice_at_char_boundary