gistfile1.diff

diff --git a/lib/rubygems/specification.rb b/lib/rubygems/specification.rb
index c40a86a..88c491d 100644
--- a/lib/rubygems/specification.rb
+++ b/lib/rubygems/specification.rb
@@ -900,7 +900,7 @@ class Gem::Specification
     return unless File.file?(file)
 
     code = if defined? Encoding
-             File.read file, :encoding => "UTF-8"
+             File.read file, :mode => 'r:UTF-8:-'
            else
              File.read file
            end
diff --git a/test/rubygems/test_gem_specification.rb b/test/rubygems/test_gem_specification.rb
index f1def67..d5f69f3 100644
--- a/test/rubygems/test_gem_specification.rb
+++ b/test/rubygems/test_gem_specification.rb
@@ -308,6 +308,25 @@ bindir:
     assert_equal @a2, spec
   end
 
+  if defined?(Encoding)
+  def test_self_load_utf8_with_ascii_encoding
+    int_enc = Encoding.default_internal
+    Encoding.default_internal = 'US-ASCII'
+
+    spec2 = @a2.dup
+    spec2.authors = ["\u5678"]
+    full_path = spec2.spec_file
+    write_file full_path do |io|
+      io.write spec2.to_ruby_for_cache
+    end
+    spec2.files.clear
+
+    assert_equal spec2, spec
+  ensure
+    Encoding.default_internal = int_enc
+  end
+  end
+
   def test_self_load_legacy_ruby
     spec = Gem::Deprecate.skip_during do
       eval LEGACY_RUBY_SPEC