diff --git a/vfs/hammer2/hammer2_msgops.c b/vfs/hammer2/hammer2_msgops.c
--- a/vfs/hammer2/hammer2_msgops.c
+++ b/vfs/hammer2/hammer2_msgops.c
@@ -69,7 +69,7 @@
 		 * a streaming transaction), we will have already closed
 		 * our end.
 		 */
-		if (msg->aux_data) {
+		if (msg->aux_data && msg->aux_size > 0) {
 			msg->aux_data[msg->aux_size - 1] = 0;
 			kprintf("DEBUGMSG: %s\n", msg->aux_data);
 		}