diff --git a/base/tcppack.c b/base/tcppack.c
index bfeb268..fcdc360 100644
--- a/base/tcppack.c
+++ b/base/tcppack.c
@@ -242,7 +242,12 @@ static int process_data_segment(conn,handler,p,stream,direction)
     long l;
 
     l=p->len - p->tcp->th_off * 4;
-    
+
+    if(l < 0) {
+	printf("Malformed packet, computed TCP segment size is negative, skipping ...\n");
+	return(0);
+    }
+
     if(stream->close){
       DBG((0,"Rejecting packet received after FIN: %u:%u(%u)",
              ntohl(p->tcp->th_seq),ntohl(p->tcp->th_seq+l),l));