diff --git a/src/include/lwip/opt.h b/src/include/lwip/opt.h
index e88a671c..4714947a 100644
--- a/src/include/lwip/opt.h
+++ b/src/include/lwip/opt.h
@@ -102,7 +102,7 @@
  * (the array of lwip-internal cyclic timers is still provided)
  * (check NO_SYS_NO_TIMERS for compatibility to old versions)
  */
-#ifndef LWIP_TIMERS || defined __DOXYGEN__
+#if !defined LWIP_TIMERS || defined __DOXYGEN__
 #ifdef NO_SYS_NO_TIMERS
 #define LWIP_TIMERS                     (!NO_SYS || (NO_SYS && !NO_SYS_NO_TIMERS))
 #else
@@ -1524,26 +1524,6 @@
  * @}
  */
 
-/*
-   ------------------------------------
-   ---------- SLIPIF options ----------
-   ------------------------------------
-*/
-/**
- * @defgroup lwip_opts_slip SLIP interface
- * @ingroup lwip_opts
- * @{
- */
-/**
- * LWIP_HAVE_SLIPIF==1: Support slip interface and slipif.c
- */
-#if !defined LWIP_HAVE_SLIPIF || defined __DOXYGEN__
-#define LWIP_HAVE_SLIPIF                0
-#endif
-/**
- * @}
- */
-
 /*
    ------------------------------------
    ---------- Thread options ----------
diff --git a/src/netif/slipif.c b/src/netif/slipif.c
index 8849cc32..f6c5d4b7 100644
--- a/src/netif/slipif.c
+++ b/src/netif/slipif.c
@@ -62,8 +62,6 @@
 #include "netif/slipif.h"
 #include "lwip/opt.h"
 
-#if LWIP_HAVE_SLIPIF
-
 #include "lwip/def.h"
 #include "lwip/pbuf.h"
 #include "lwip/stats.h"
@@ -555,5 +553,3 @@ slipif_received_bytes(struct netif *netif, u8_t *data, u8_t len)
   }
 }
 #endif /* SLIP_RX_FROM_ISR */
-
-#endif /* LWIP_HAVE_SLIPIF */