Index: head/sys/dev/hyperv/vmbus/vmbus_chan.c
===================================================================
--- head/sys/dev/hyperv/vmbus/vmbus_chan.c
+++ head/sys/dev/hyperv/vmbus/vmbus_chan.c
@@ -502,11 +502,7 @@
 	int page_count, range_len, i, cnt, error;
 	uint64_t page_id;
 
-	/*
-	 * Reset GPADL, so that the result would consistent, if error
-	 * happened later on.
-	 */
-	*gpadl0 = 0;
+	KASSERT(*gpadl0 == 0, ("GPADL is not zero"));
 
 	/*
 	 * Preliminary checks.
@@ -652,6 +648,8 @@
 	struct vmbus_chanmsg_gpadl_disconn *req;
 	int error;
 
+	KASSERT(gpadl != 0, ("GPADL is zero"));
+
 	mh = vmbus_msghc_get(sc, sizeof(*req));
 	if (mh == NULL) {
 		vmbus_chan_printf(chan,