diff --git a/uip/uip-fw.c b/uip/uip-fw.c
index 4b669798..ddc9de64 100644
--- a/uip/uip-fw.c
+++ b/uip/uip-fw.c
@@ -64,6 +64,8 @@
 
 #include "../rtl837x_common.h"
 
+#if UIP_FORWARDING
+
 /*
  * The list of registered network interfaces.
  */
@@ -535,3 +537,5 @@ uip_fw_periodic(void)
   }
 }
 /*------------------------------------------------------------------------------*/
+
+#endif /* UIP_FORWARDING */
diff --git a/uip/uip-neighbor.c b/uip/uip-neighbor.c
index 0795cef8..cc3ab994 100644
--- a/uip/uip-neighbor.c
+++ b/uip/uip-neighbor.c
@@ -43,6 +43,8 @@
 #include "uip-neighbor.h"
 #include "../rtl837x_common.h"
 
+#if UIP_CONF_IPV6
+
 #pragma codeseg BANK1
 #pragma constseg BANK1
 
@@ -170,3 +172,5 @@ uip_neighbor_lookup(__xdata uip_ipaddr_t ipaddr)
   return NULL;
 }
 /*---------------------------------------------------------------------------*/
+
+#endif /* UIP_CONF_IPV6 */
diff --git a/uip/uipopt.h b/uip/uipopt.h
index 20aec637..620d6054 100644
--- a/uip/uipopt.h
+++ b/uip/uipopt.h
@@ -464,6 +464,20 @@ extern __xdata uint8_t uip_buf[UIP_CONF_BUFFER_SIZE+2];
 #define UIP_BROADCAST UIP_CONF_BROADCAST
 #endif /* UIP_CONF_BROADCAST */
 
+/**
+ * Build the IP forwarding module.
+ *
+ * uip-fw.c forwards packets between several network interfaces. A
+ * single-interface device does not call it and should not pay for it.
+ *
+ * \hideinitializer
+ */
+#ifndef UIP_CONF_FORWARDING
+#define UIP_FORWARDING 0
+#else /* UIP_CONF_FORWARDING */
+#define UIP_FORWARDING UIP_CONF_FORWARDING
+#endif /* UIP_CONF_FORWARDING */
+
 /**
  * Print out a uIP log message.
  *