diff --git a/src/include/lwip/tcp.h b/src/include/lwip/tcp.h
index 34d1c101..74b08ae4 100644
--- a/src/include/lwip/tcp.h
+++ b/src/include/lwip/tcp.h
@@ -42,6 +42,7 @@
 
 #if LWIP_TCP /* don't build if not configured for use in lwipopts.h */
 
+#include "lwip/tcpbase.h"
 #include "lwip/mem.h"
 #include "lwip/pbuf.h"
 #include "lwip/ip.h"
@@ -136,13 +137,11 @@ typedef err_t (*tcp_connected_fn)(void *arg, struct tcp_pcb *tpcb, err_t err);
 #define SND_WND_SCALE(pcb, wnd) (((wnd) << (pcb)->snd_scale))
 #define TCPWND16(x)             ((u16_t)LWIP_MIN((x), 0xFFFF))
 #define TCP_WND_MAX(pcb)        ((tcpwnd_size_t)(((pcb)->flags & TF_WND_SCALE) ? TCP_WND : TCPWND16(TCP_WND)))
-typedef u32_t tcpwnd_size_t;
 #else
 #define RCV_WND_SCALE(pcb, wnd) (wnd)
 #define SND_WND_SCALE(pcb, wnd) (wnd)
 #define TCPWND16(x)             (x)
 #define TCP_WND_MAX(pcb)        TCP_WND
-typedef u16_t tcpwnd_size_t;
 #endif
 
 #if LWIP_WND_SCALE || TCP_LISTEN_BACKLOG || LWIP_TCP_TIMESTAMPS
@@ -151,20 +150,6 @@ typedef u16_t tcpflags_t;
 typedef u8_t tcpflags_t;
 #endif
 
-enum tcp_state {
-  CLOSED      = 0,
-  LISTEN      = 1,
-  SYN_SENT    = 2,
-  SYN_RCVD    = 3,
-  ESTABLISHED = 4,
-  FIN_WAIT_1  = 5,
-  FIN_WAIT_2  = 6,
-  CLOSE_WAIT  = 7,
-  CLOSING     = 8,
-  LAST_ACK    = 9,
-  TIME_WAIT   = 10
-};
-
 /**
  * members common to struct tcp_pcb and struct tcp_listen_pcb
  */
@@ -403,19 +388,11 @@ void             tcp_abort (struct tcp_pcb *pcb);
 err_t            tcp_close   (struct tcp_pcb *pcb);
 err_t            tcp_shutdown(struct tcp_pcb *pcb, int shut_rx, int shut_tx);
 
-/* Flags for "apiflags" parameter in tcp_write */
-#define TCP_WRITE_FLAG_COPY 0x01
-#define TCP_WRITE_FLAG_MORE 0x02
-
 err_t            tcp_write   (struct tcp_pcb *pcb, const void *dataptr, u16_t len,
                               u8_t apiflags);
 
 void             tcp_setprio (struct tcp_pcb *pcb, u8_t prio);
 
-#define TCP_PRIO_MIN    1
-#define TCP_PRIO_NORMAL 64
-#define TCP_PRIO_MAX    127
-
 err_t            tcp_output  (struct tcp_pcb *pcb);
 
 
diff --git a/src/include/lwip/tcpbase.h b/src/include/lwip/tcpbase.h
new file mode 100644
index 00000000..f30664b0
--- /dev/null
+++ b/src/include/lwip/tcpbase.h
@@ -0,0 +1,84 @@
+/**
+ * @file
+ * Base TCP API definitions shared by TCP and ALTCP\n
+ * See also @ref tcp_raw
+ */
+
+/*
+ * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
+ * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+ * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ *
+ * This file is part of the lwIP TCP/IP stack.
+ *
+ * Author: Adam Dunkels <adam@sics.se>
+ *
+ */
+#ifndef LWIP_HDR_TCPBASE_H
+#define LWIP_HDR_TCPBASE_H
+
+#include "lwip/opt.h"
+
+#if LWIP_TCP /* don't build if not configured for use in lwipopts.h */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+#if LWIP_WND_SCALE
+typedef u32_t tcpwnd_size_t;
+#else
+typedef u16_t tcpwnd_size_t;
+#endif
+
+enum tcp_state {
+  CLOSED      = 0,
+  LISTEN      = 1,
+  SYN_SENT    = 2,
+  SYN_RCVD    = 3,
+  ESTABLISHED = 4,
+  FIN_WAIT_1  = 5,
+  FIN_WAIT_2  = 6,
+  CLOSE_WAIT  = 7,
+  CLOSING     = 8,
+  LAST_ACK    = 9,
+  TIME_WAIT   = 10
+};
+
+/* Flags for "apiflags" parameter in tcp_write */
+#define TCP_WRITE_FLAG_COPY 0x01
+#define TCP_WRITE_FLAG_MORE 0x02
+
+#define TCP_PRIO_MIN    1
+#define TCP_PRIO_NORMAL 64
+#define TCP_PRIO_MAX    127
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* LWIP_TCP */
+
+#endif /* LWIP_HDR_TCPBASE_H */