diff --git a/src/core/init.c b/src/core/init.c
index b3737a35..3620e1d4 100644
--- a/src/core/init.c
+++ b/src/core/init.c
@@ -237,8 +237,9 @@ PACK_STRUCT_END
 #error "NETCONN_MORE != TCP_WRITE_FLAG_MORE"
 #endif
 #endif /* LWIP_NETCONN && LWIP_TCP */
-#if LWIP_SOCKET
-#endif /* LWIP_SOCKET */
+#if LWIP_NETCONN_FULLDUPLEX && !LWIP_NETCONN_SEM_PER_THREAD
+#error "For LWIP_NETCONN_FULLDUPLEX to work, LWIP_NETCONN_SEM_PER_THREAD is required"
+#endif
 
 
 /* Compile-time checks for deprecated options.
diff --git a/src/include/lwip/opt.h b/src/include/lwip/opt.h
index 10625c72..1e10cc6a 100644
--- a/src/include/lwip/opt.h
+++ b/src/include/lwip/opt.h
@@ -1920,11 +1920,8 @@
 
 /** LWIP_NETCONN_FULLDUPLEX==1: Enable code that allows reading from one thread,
  * writing from a 2nd thread and closing from a 3rd thread at the same time.
- * ATTENTION: This is currently really alpha! Some requirements:
- * - LWIP_NETCONN_SEM_PER_THREAD==1 is required to use one socket/netconn from
- *   multiple threads at once
- * - sys_mbox_free() has to unblock receive tasks waiting on recvmbox/acceptmbox
- *   and prevent a task pending on this during/after deletion
+ * LWIP_NETCONN_SEM_PER_THREAD==1 is required to use one socket/netconn from
+ * multiple threads at once!
  */
 #if !defined LWIP_NETCONN_FULLDUPLEX || defined __DOXYGEN__
 #define LWIP_NETCONN_FULLDUPLEX         0