diff --git a/scripts/kwboot.c b/scripts/kwboot.c
index 33c94b3a8..81da3e81b 100644
--- a/scripts/kwboot.c
+++ b/scripts/kwboot.c
@@ -334,6 +334,7 @@ kwboot_xm_makeblock(struct kwboot_block *block, const void *data,
 	size_t n;
 	int i;
 
+	block->soh = SOH;
 	block->pnum = pnum;
 	block->_pnum = ~block->pnum;