diff --git a/arch/x86/include/asm/bootparam_utils.h b/arch/x86/include/asm/bootparam_utils.h
index 5b5e9cb..ff808ef 100644
--- a/arch/x86/include/asm/bootparam_utils.h
+++ b/arch/x86/include/asm/bootparam_utils.h
@@ -14,13 +14,15 @@
  * analysis of kexec-tools; if other broken bootloaders initialize a
  * different set of fields we will need to figure out how to disambiguate.
  *
+ * Note: efi_info is commonly left uninitialized, but that field has a
+ * private magic, so it is better to leave it unchanged.
  */
 static void sanitize_boot_params(struct boot_params *boot_params)
 {
 	if (boot_params->sentinel) {
 		/*fields in boot_params are not valid, clear them */
 		memset(&boot_params->olpc_ofw_header, 0,
-		       (char *)&boot_params->alt_mem_k -
+		       (char *)&boot_params->efi_info -
 			(char *)&boot_params->olpc_ofw_header);
 		memset(&boot_params->kbd_status, 0,
 		       (char *)&boot_params->hdr -