diff --git a/src/include/lwip/opt.h b/src/include/lwip/opt.h
index 236ec0c3..92cbf0f9 100644
--- a/src/include/lwip/opt.h
+++ b/src/include/lwip/opt.h
@@ -448,13 +448,19 @@
 #define MEMP_NUM_IGMP_GROUP             8
 #endif
 
+/**
+ * The number of sys timeouts used by the core stack (not apps)
+ * The default number of timeouts is calculated here for all enabled modules.
+ */
+#define LWIP_NUM_SYS_TIMEOUT_INTERNAL   (LWIP_TCP + IP_REASSEMBLY + LWIP_ARP + (2*LWIP_DHCP) + LWIP_AUTOIP + LWIP_IGMP + LWIP_DNS + (PPP_SUPPORT*6*MEMP_NUM_PPP_PCB) + (LWIP_IPV6 ? (1 + LWIP_IPV6_REASS + LWIP_IPV6_MLD) : 0))
+
 /**
  * MEMP_NUM_SYS_TIMEOUT: the number of simultaneously active timeouts.
  * The default number of timeouts is calculated here for all enabled modules.
  * The formula expects settings to be either '0' or '1'.
  */
 #if !defined MEMP_NUM_SYS_TIMEOUT || defined __DOXYGEN__
-#define MEMP_NUM_SYS_TIMEOUT            (LWIP_TCP + IP_REASSEMBLY + LWIP_ARP + (2*LWIP_DHCP) + LWIP_AUTOIP + LWIP_IGMP + LWIP_DNS + (PPP_SUPPORT*6*MEMP_NUM_PPP_PCB) + (LWIP_IPV6 ? (1 + LWIP_IPV6_REASS + LWIP_IPV6_MLD) : 0))
+#define MEMP_NUM_SYS_TIMEOUT            LWIP_NUM_SYS_TIMEOUT_INTERNAL
 #endif
 
 /**