diff --git a/library/stringio/binmode_spec.rb b/library/stringio/binmode_spec.rb
index 853d9c9bd..9e92c6381 100644
--- a/library/stringio/binmode_spec.rb
+++ b/library/stringio/binmode_spec.rb
@@ -3,7 +3,7 @@
 
 describe "StringIO#binmode" do
   it "returns self" do
-    io = StringIO.new("example")
+    io = StringIO.new(+"example")
     io.binmode.should equal(io)
   end