1 files changed, 7 insertions, 0 deletions
diff --git a/spec/ruby/command_line/dash_upper_u_spec.rb b/spec/ruby/command_line/dash_upper_u_spec.rb
index d62718b095..15854e7b73 100644
--- a/spec/ruby/command_line/dash_upper_u_spec.rb
+++ b/spec/ruby/command_line/dash_upper_u_spec.rb
@@ -6,6 +6,13 @@ describe "ruby -U" do
               options: '-U').should == 'UTF-8'
   end
 
+  it "sets Encoding.default_internal to UTF-8 when RUBYOPT is empty or only spaces" do
+    ruby_exe('p Encoding.default_internal',
+             options: '-U', env: { 'RUBYOPT' => '' }).should == "#<Encoding:UTF-8>\n"
+    ruby_exe('p Encoding.default_internal',
+             options: '-U', env: { 'RUBYOPT' => '  ' }).should == "#<Encoding:UTF-8>\n"
+  end
+
   it "does nothing different if specified multiple times" do
      ruby_exe('print Encoding.default_internal.name',
               options: '-U -U').should == 'UTF-8'