diff --git a/library/stringscanner/shared/concat.rb b/library/stringscanner/shared/concat.rb
index 28788d3ff1..214455d1b9 100644
--- a/library/stringscanner/shared/concat.rb
+++ b/library/stringscanner/shared/concat.rb
@@ -25,6 +25,6 @@
     x = mock('x')
     x.should_not_receive(:to_int)
 
-    lambda { "".send(@method, x) }.should raise_error(TypeError)
+    lambda { StringScanner.new("").send(@method, x) }.should raise_error(TypeError)
   end
 end