diff --git a/CHANGELOG b/CHANGELOG
index 8f771703..eefa9135 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -25,6 +25,10 @@ HISTORY
 
   ++ Bugfixes:
 
+  2009-08-23 Simon Goldschmidt
+  * opt.h, init.c: bug #26649: TCP fails when TCP_MSS > TCP_SND_BUF
+    Fixed wrong parenthesis, added check in init.c
+
   2009-08-23 Simon Goldschmidt
   * ppp.c: bug #27266: wait-state debug message in pppMain occurs every ms
 
diff --git a/src/core/init.c b/src/core/init.c
index 277811a6..ff679738 100644
--- a/src/core/init.c
+++ b/src/core/init.c
@@ -208,6 +208,8 @@ lwip_sanity_check(void)
 #if LWIP_TCP
   if (MEMP_NUM_TCP_SEG < TCP_SND_QUEUELEN)
     LWIP_PLATFORM_DIAG(("lwip_sanity_check: WARNING: MEMP_NUM_TCP_SEG should be at least as big as TCP_SND_QUEUELEN\n"));
+  if (TCP_SND_BUF < 2 * TCP_MSS)
+    LWIP_PLATFORM_DIAG(("lwip_sanity_check: WARNING: TCP_SND_BUF must be at least as much as (2 * TCP_MSS) for things to work smoothly\n"));
   if (TCP_SND_QUEUELEN < (2 * (TCP_SND_BUF/TCP_MSS)))
     LWIP_PLATFORM_DIAG(("lwip_sanity_check: WARNING: TCP_SND_QUEUELEN must be at least as much as (2 * TCP_SND_BUF/TCP_MSS) for things to work\n"));
   if (TCP_SNDLOWAT > TCP_SND_BUF)
diff --git a/src/include/lwip/opt.h b/src/include/lwip/opt.h
index e8bd8b89..e389d4e3 100644
--- a/src/include/lwip/opt.h
+++ b/src/include/lwip/opt.h
@@ -803,7 +803,7 @@
  * as much as (2 * TCP_SND_BUF/TCP_MSS) for things to work.
  */
 #ifndef TCP_SND_QUEUELEN
-#define TCP_SND_QUEUELEN                (4 * (TCP_SND_BUF/TCP_MSS))
+#define TCP_SND_QUEUELEN                (4 * (TCP_SND_BUF)/(TCP_MSS))
 #endif
 
 /**
@@ -812,7 +812,7 @@
  * TCP snd_buf for select to return writable.
  */
 #ifndef TCP_SNDLOWAT
-#define TCP_SNDLOWAT                    (TCP_SND_BUF/2)
+#define TCP_SNDLOWAT                    ((TCP_SND_BUF)/2)
 #endif
 
 /**