1 files changed, 8 insertions, 0 deletions
diff --git a/spec/ruby/core/string/index_spec.rb b/spec/ruby/core/string/index_spec.rb
index 5d77a88e4e..2eeee9be87 100644
--- a/spec/ruby/core/string/index_spec.rb
+++ b/spec/ruby/core/string/index_spec.rb
@@ -159,6 +159,14 @@ describe "String#index with String" do
       "あれ".index char
     end.should raise_error(Encoding::CompatibilityError)
   end
+
+  it "handles a substring in a superset encoding" do
+    'abc'.force_encoding(Encoding::US_ASCII).index('é').should == nil
+  end
+
+  it "handles a substring in a subset encoding" do
+    'été'.index('t'.force_encoding(Encoding::US_ASCII)).should == 1
+  end
 end
 
 describe "String#index with Regexp" do