diff --git a/CHANGELOG b/CHANGELOG
index 21a85c94..b427d9c4 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -6,7 +6,7 @@ HISTORY
 
   ++ New features:
 
-  2016-02-22: Ivan Delamer:
+  2016-02-22: Ivan Delamer
   * Initial 6LoWPAN support
 
   2015-12-26: Martin Hentschel and Dirk Ziegelmeier
@@ -302,6 +302,9 @@ HISTORY
 
   ++ Bugfixes:
 
+  2016-03-16: Deomid Ryabkov
+  * tcp_out.c: fixed bug #46384 Segment size calculation bug with MSS != TCP_MSS
+
   2016-03-05: Simon Goldschmidt
   * err.h/.c, sockets.c: ERR_IF is not necessarily a fatal error
 
diff --git a/src/core/tcp_out.c b/src/core/tcp_out.c
index fa8d77fb..a7b05954 100644
--- a/src/core/tcp_out.c
+++ b/src/core/tcp_out.c
@@ -469,7 +469,7 @@ tcp_write(struct tcp_pcb *pcb, const void *arg, u16_t len, u8_t apiflags)
     if (oversize > 0) {
       LWIP_ASSERT("inconsistent oversize vs. space", oversize_used <= space);
       seg = last_unsent;
-      oversize_used = oversize < len ? oversize : len;
+      oversize_used = LWIP_MIN(space, LWIP_MIN(oversize, len));
       pos += oversize_used;
       oversize -= oversize_used;
       space -= oversize_used;