diff --git a/sys/kern/kern_ktrace.c b/sys/kern/kern_ktrace.c
index 49e9dff4e643..c2f747c474de 100644
--- a/sys/kern/kern_ktrace.c
+++ b/sys/kern/kern_ktrace.c
@@ -229,8 +229,7 @@ ktrace_init(void *dummy)
 		    M_ZERO);
 		STAILQ_INSERT_HEAD(&ktr_free, req, ktr_list);
 	}
-	ast_register(TDA_KTRACE, ASTR_UNCOND, 0, ast_ktrace);
-
+	ast_register(TDA_KTRACE, ASTR_ASTF_REQUIRED, 0, ast_ktrace);
 }
 SYSINIT(ktrace_init, SI_SUB_KTRACE, SI_ORDER_ANY, ktrace_init, NULL);