diff --git a/sys/cddl/dev/kinst/trampoline.c b/sys/cddl/dev/kinst/trampoline.c
--- a/sys/cddl/dev/kinst/trampoline.c
+++ b/sys/cddl/dev/kinst/trampoline.c
@@ -163,6 +163,8 @@
 	struct trampchunk *chunk;
 	int off;
 
+	sx_assert(&kinst_tramp_sx, SX_XLOCKED);
+
 	if (tramp == NULL)
 		return;