Don't use normal mode mappings in vimscript

autoload/do.vim

@@ -59,14 +59,14 @@ endfunction
 function! do#rename_include_guard(old)
   " Prompt for new guard name
   let l:new = input('Rename include guard: ', a:old)
-  " Set a mark to jump back to
-  normal mr
+  " Get the current position
+  let l:pos = getpos('.')
   " Replace the old guard name with the new one
   exec '%s/\(#ifndef\|#define\|#endif\s\+\/\/\)\s\+\zs'.a:old.'/'.l:new.'/g'
   " Stop highlighting search results
   nohlsearch
-  " Jump back to the set mark
-  normal 'r
+  " Jump back to the start position
+  call setpos('.', l:pos)
 endfunction
 
 " Setup and start a debugging command.