diff --git a/src/core/dhcp.c b/src/core/dhcp.c
index 2e578205..69337567 100644
--- a/src/core/dhcp.c
+++ b/src/core/dhcp.c
@@ -100,7 +100,6 @@ static void dhcp_check(struct netif *netif);
 static void dhcp_bind(struct netif *netif);
 static err_t dhcp_decline(struct netif *netif);
 static err_t dhcp_rebind(struct netif *netif);
-static err_t dhcp_release(struct netif *netif);
 static void dhcp_set_state(struct dhcp *dhcp, unsigned char new_state);
 
 /** receive, unfold, parse and free incoming messages */
@@ -925,7 +924,7 @@ static err_t dhcp_rebind(struct netif *netif)
  *
  * @param netif network interface which must release its lease
  */
-static err_t dhcp_release(struct netif *netif)
+err_t dhcp_release(struct netif *netif)
 {
   struct dhcp *dhcp = netif->dhcp;
   err_t result;
diff --git a/src/include/lwip/dhcp.h b/src/include/lwip/dhcp.h
index 6cb5cd43..bfe753f2 100644
--- a/src/include/lwip/dhcp.h
+++ b/src/include/lwip/dhcp.h
@@ -86,8 +86,12 @@ struct dhcp_msg
   PACK_STRUCT_FIELD(u8_t file[DHCP_FILE_LEN]);
   PACK_STRUCT_FIELD(u32_t cookie);
 #define DHCP_MIN_OPTIONS_LEN 68U
+/** make sure user does not configure this too small */
+#if ((defined(DHCP_OPTIONS_LEN)) && (DHCP_OPTIONS_LEN < DHCP_MIN_OPTIONS_LEN))
+#  undef DHCP_OPTIONS_LEN
+#endif
 /** allow this to be configured in lwipopts.h, but not too small */
-#if ((!defined(DHCP_OPTIONS_LEN)) || (DHCP_OPTIONS_LEN < DHCP_MIN_OPTIONS_LEN))
+#if (!defined(DHCP_OPTIONS_LEN))
 /** set this to be sufficient for your options in outgoing DHCP msgs */
 #  define DHCP_OPTIONS_LEN DHCP_MIN_OPTIONS_LEN
 #endif
@@ -100,11 +104,13 @@ PACK_STRUCT_END
 
 /** start DHCP configuration */
 err_t dhcp_start(struct netif *netif);
+/** enforce early lease renewal (not needed normally)*/
+err_t dhcp_renew(struct netif *netif);
+/** release the DHCP lease, usually called before dhcp_stop()*/
+err_t dhcp_release(struct netif *netif);
 /** stop DHCP configuration */
 void dhcp_stop(struct netif *netif);
-/** enforce lease renewal */
-err_t dhcp_renew(struct netif *netif);
-/** inform server of our IP address */
+/** inform server of our manual IP address */
 void dhcp_inform(struct netif *netif);
 
 /** if enabled, check whether the offered IP address is not in use, using ARP */