diff --git a/grub-core/loader/arm64/xen_boot.c b/grub-core/loader/arm64/xen_boot.c
index a914eb8e2..8ae43d7e8 100644
--- a/grub-core/loader/arm64/xen_boot.c
+++ b/grub-core/loader/arm64/xen_boot.c
@@ -156,7 +156,7 @@ prepare_xen_module_params (struct xen_boot_binary *module, void *xen_boot_fdt)
       grub_fdt_add_subnode (xen_boot_fdt, chosen_node, module_name);
 
   retval = grub_fdt_set_prop (xen_boot_fdt, module_node, "compatible",
-			      MODULE_CUSTOM_COMPATIBLE, sizeof(MODULE_CUSTOM_COMPATIBLE) - 1);
+			      MODULE_CUSTOM_COMPATIBLE, sizeof(MODULE_CUSTOM_COMPATIBLE));
   if (retval)
     return grub_error (GRUB_ERR_IO, "failed to update FDT");