diff --git a/util/grub-install.c b/util/grub-install.c
index 566272600..df5c7e520 100644
--- a/util/grub-install.c
+++ b/util/grub-install.c
@@ -1727,7 +1727,7 @@ main (int argc, char *argv[])
 	  grub_elf = grub_util_path_concat (2, core_services, "grub.elf");
 	  grub_install_copy_file (imgfile, grub_elf, 1);
 
-	  f = grub_util_fopen (mach_kernel, "r+");
+	  f = grub_util_fopen (mach_kernel, "a+");
 	  if (!f)
 	    grub_util_error (_("Can't create file: %s"), strerror (errno));
 	  fclose (f);