diff --git a/library/date/minus_month_spec.rb b/library/date/minus_month_spec.rb
index 78b7d654fb..130a1bb32a 100644
--- a/library/date/minus_month_spec.rb
+++ b/library/date/minus_month_spec.rb
@@ -14,10 +14,10 @@
   end
 
   it "raises an error on non numeric parameters" do
-    lambda { Date.civil(2007,2,27) << :hello }.should raise_error(NoMethodError)
-    lambda { Date.civil(2007,2,27) << "hello" }.should raise_error(NoMethodError)
-    lambda { Date.civil(2007,2,27) << Date.new }.should raise_error(NoMethodError)
-    lambda { Date.civil(2007,2,27) << Object.new }.should raise_error(NoMethodError)
+    lambda { Date.civil(2007,2,27) << :hello }.should raise_error #(TypeError)
+    lambda { Date.civil(2007,2,27) << "hello" }.should raise_error #(TypeError)
+    lambda { Date.civil(2007,2,27) << Date.new }.should raise_error #(TypeError)
+    lambda { Date.civil(2007,2,27) << Object.new }.should raise_error #(TypeError)
   end
 
 end