Index: sys/opencrypto/crypto.c
===================================================================
--- sys/opencrypto/crypto.c
+++ sys/opencrypto/crypto.c
@@ -1352,7 +1352,8 @@
 		KASSERT(crp->crp_payload_output_start == 0,
 		    ("payload output start non-zero without output buffer"));
 	} else {
-		KASSERT(crp->crp_payload_output_start < olen,
+		KASSERT(crp->crp_payload_output_start == 0 ||
+		    crp->crp_payload_output_start < olen,
 		    ("invalid payload output start"));
 		KASSERT(crp->crp_payload_output_start +
 		    crp->crp_payload_length <= olen,