diff --git a/CHANGELOG b/CHANGELOG
index c42f4602..3191a970 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -96,6 +96,10 @@ HISTORY
 
  ++ Bugfixes:
 
+  2014-02-20: Simon Goldschmidt
+  * tcp_out.c: fixed bug #39683 Assertion "seg->tcphdr not aligned" failed with
+    MEM_ALIGNMENT = 8
+
   2014-02-20: Simon Goldschmidt
   * sockets.c: fixed bug #39882 No function shall set errno to 0
 
diff --git a/src/core/tcp_out.c b/src/core/tcp_out.c
index bc67e09f..6eb2d64f 100644
--- a/src/core/tcp_out.c
+++ b/src/core/tcp_out.c
@@ -789,7 +789,7 @@ tcp_enqueue_flags(struct tcp_pcb *pcb, u8_t flags)
     TCP_STATS_INC(tcp.memerr);
     return ERR_MEM;
   }
-  LWIP_ASSERT("seg->tcphdr not aligned", ((mem_ptr_t)seg->tcphdr % MEM_ALIGNMENT) == 0);
+  LWIP_ASSERT("seg->tcphdr not aligned", ((mem_ptr_t)seg->tcphdr % 4) == 0);
   LWIP_ASSERT("tcp_enqueue_flags: invalid segment length", seg->len == 0);
 
   LWIP_DEBUGF(TCP_OUTPUT_DEBUG | LWIP_DBG_TRACE,