diff --git a/CHANGELOG b/CHANGELOG
index 3cc39187..19c5ae82 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -46,6 +46,10 @@ HISTORY
 
   ++ Bugfixes:
 
+  2009-11-26: Simon Goldschmidt
+  * tcp.h, sockets.c: Fixed bug #28099: API required to disable Nagle
+    algorithm at PCB level
+
   2009-11-22: Simon Goldschmidt
   * tcp_out.c: Fixed bug #27905: FIN isn't combined with data on unsent
 
diff --git a/src/api/sockets.c b/src/api/sockets.c
index 34ef098b..1d50aebb 100644
--- a/src/api/sockets.c
+++ b/src/api/sockets.c
@@ -1492,7 +1492,7 @@ lwip_getsockopt_internal(void *arg)
   case IPPROTO_TCP:
     switch (optname) {
     case TCP_NODELAY:
-      *(int*)optval = (sock->conn->pcb.tcp->flags & TF_NODELAY);
+      *(int*)optval = tcp_nagle_enabled(sock->conn->pcb.tcp);
       LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_TCP, TCP_NODELAY) = %s\n",
                   s, (*(int*)optval)?"on":"off") );
       break;
@@ -1853,9 +1853,9 @@ lwip_setsockopt_internal(void *arg)
     switch (optname) {
     case TCP_NODELAY:
       if (*(int*)optval) {
-        sock->conn->pcb.tcp->flags |= TF_NODELAY;
+        tcp_nagle_enable(sock->conn->pcb.tcp);
       } else {
-        sock->conn->pcb.tcp->flags &= ~TF_NODELAY;
+        tcp_nagle_disable(sock->conn->pcb.tcp);
       }
       LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_TCP, TCP_NODELAY) -> %s\n",
                   s, (*(int *)optval)?"on":"off") );
diff --git a/src/include/lwip/tcp.h b/src/include/lwip/tcp.h
index 9a34872b..3d309578 100644
--- a/src/include/lwip/tcp.h
+++ b/src/include/lwip/tcp.h
@@ -78,6 +78,9 @@ void             tcp_err     (struct tcp_pcb *pcb,
 
 #define          tcp_mss(pcb)      ((pcb)->mss)
 #define          tcp_sndbuf(pcb)   ((pcb)->snd_buf)
+#define          tcp_nagle_enable(pcb)  ((pcb)->flags |= TF_NODELAY)
+#define          tcp_nagle_disable(pcb) ((pcb)->flags &= ~TF_NODELAY)
+#define          tcp_nagle_enabled(pcb) (((pcb)->flags & TF_NODELAY) != 0)
 
 #if TCP_LISTEN_BACKLOG
 #define          tcp_accepted(pcb) (((struct tcp_pcb_listen *)(pcb))->accepts_pending--)
@@ -137,7 +140,7 @@ u32_t            tcp_update_rcv_ann_wnd(struct tcp_pcb *pcb);
  *   than one unsent segment - with lwIP, this can happen although unsent->len < mss)
  */
 #define tcp_do_output_nagle(tpcb) ((((tpcb)->unacked == NULL) || \
-                            ((tpcb)->flags & TF_NODELAY) || \
+                            (tcp_nagle_enabled(tpcb)) || \
                             (((tpcb)->unsent != NULL) && (((tpcb)->unsent->next != NULL) || \
                               ((tpcb)->unsent->len >= (tpcb)->mss))) \
                             ) ? 1 : 0)