diff --git a/doc/plan.org b/doc/plan.org
index 1972b35..a848bad 100644
--- a/doc/plan.org
+++ b/doc/plan.org
@@ -5295,7 +5295,7 @@ p4@ubuntu:~/master-thesis/bin$ mx h3 "echo V4-OK | socat - UDP:10.1.1.1:2342"
 **** DONE Result: arp (partly?) missing?
      CLOSED: [2019-07-16 Tue 11:00]
 
-**** TODO Result: udp checksum wrong
+**** Result: udp checksum wrong
      - should be: 0xd84b
      - is: 0xd84c
 
@@ -5309,7 +5309,8 @@ This is used to correct endianness!
 
 -> not needed in our case
 
-*** TODO 2019-07-16: Wraptest in P4
+*** DONE 2019-07-16: Wraptest in P4
+    CLOSED: [2019-07-16 Tue 12:09]
 #+BEGIN_CENTER
  mx h3
 arp -s 10.0.0.2 00:00:0a:00:00:02
@@ -5328,6 +5329,12 @@ Result on the wire of the wraptest:
 -> as expected
 
 Thus carryover is already implemented. Try to use 16 bit ints
+
+*** TODO 2019-07-16: naive approach
+Gives off-by-one in udp, sometimes!
+
+10:08:52.626713 IP6 (hlim 64, next-header UDP (17) payload length: 14) 2001:db8:1::a00:1.51345 > 2001:db8::1.2342: [bad udp cks
+
 ** The NetPFGA saga
 Problems encountered:
 - The logfile for a compile run is 10k+ lines
diff --git a/p4src/actions_delta_checksum.p4 b/p4src/actions_delta_checksum.p4
index a34c719..c258d18 100644
--- a/p4src/actions_delta_checksum.p4
+++ b/p4src/actions_delta_checksum.p4
@@ -53,7 +53,9 @@ action delta_prepare()
 action delta_udp_from_v4_to_v6()
 {
     delta_prepare();
-    hdr.udp.checksum = hdr.udp.checksum + meta.v6sum - meta.v4sum;
+    hdr.udp.checksum = meta.v6sum;
+//    hdr.udp.checksum = meta.v4sum;
+//    hdr.udp.checksum = hdr.udp.checksum + meta.v6sum - meta.v4sum;
 }
 
 action delta_tcp_from_v4_to_v6()