diff --git a/source/smbd/reply.c b/source/smbd/reply.c
index 0de0e15274c..9d5d34e410f 100644
--- a/source/smbd/reply.c
+++ b/source/smbd/reply.c
@@ -3722,6 +3722,13 @@ int reply_lockingX(connection_struct *conn, char *inbuf,char *outbuf,int length,
 	CHECK_FSP(fsp,conn);
 	
 	data = smb_buf(inbuf);
+
+	if (locktype & (LOCKING_ANDX_CANCEL_LOCK | LOCKING_ANDX_CHANGE_LOCKTYPE)) {
+		/* we don't support these - and CANCEL_LOCK makes w2k
+		   and XP reboot so I don't really want to be
+		   compatible! (tridge) */
+		return ERROR_NT(NT_STATUS_NOT_SUPPORTED);
+	}
 	
 	/* Check if this is an oplock break on a file
 	   we have granted an oplock on.