diff --git a/CHANGELOG b/CHANGELOG
index 4ea5aa75..44695236 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -238,6 +238,10 @@ HISTORY
 
   ++ Bug fixes:
 
+  2007-06-28 Simon Goldschmidt
+  * tcp.h: Fixed bug #20287: Fixed nagle algorithm (sending was done too early if
+    a segment contained chained pbufs)
+
   2007-06-28 Frédéric Bernon
   * autoip.c: replace most of rand() calls by a macro LWIP_AUTOIP_RAND which compute
     a "pseudo-random" value based on netif's MAC and some autoip fields. It's always
diff --git a/src/include/lwip/tcp.h b/src/include/lwip/tcp.h
index 16e75696..668800ad 100644
--- a/src/include/lwip/tcp.h
+++ b/src/include/lwip/tcp.h
@@ -119,7 +119,7 @@ void             tcp_rexmit_rto  (struct tcp_pcb *pcb);
  */
 #define tcp_output_nagle(tpcb) ((((tpcb)->unacked == NULL) || \
                                  ((tpcb)->flags & TF_NODELAY) || \
-                                 ((tpcb)->snd_queuelen > 1)) ? \
+                                 (((tpcb)->unsent != NULL) && ((tpcb)->unsent->next != NULL))) ? \
                                 tcp_output(tpcb) : ERR_OK)