diff --git a/docs/The_fOOrth_User_Guide.odt b/docs/The_fOOrth_User_Guide.odt
index f3fcf45..ad9e209 100644
Binary files a/docs/The_fOOrth_User_Guide.odt and b/docs/The_fOOrth_User_Guide.odt differ
diff --git a/lib/fOOrth/compiler.rb b/lib/fOOrth/compiler.rb
index 5728c0e..321d8c5 100644
--- a/lib/fOOrth/compiler.rb
+++ b/lib/fOOrth/compiler.rb
@@ -48,6 +48,8 @@ module XfOOrth
     def <<(text)
       dbg_puts "  Append=#{text.inspect}"
       @buffer << text
+    rescue NoMethodError
+      error "F14: The current mode does not allow code to be appended."
     end
 
     #Execute code from the interactive console.