diff --git a/.github/workflows/ci-linux.yml b/.github/workflows/ci-linux.yml
index 8b5d9bfa..1686e2e9 100644
--- a/.github/workflows/ci-linux.yml
+++ b/.github/workflows/ci-linux.yml
@@ -51,7 +51,7 @@ jobs:
       run: |
         cp ${CONTRIB}/examples/example_app/lwipcfg.h.example ${CONTRIB}/examples/example_app/lwipcfg.h
         cd ${CONTRIB}/ports/unix/example_app
-        export CFLAGS="-DESP_LWIP=LWIP_NETCONN_FULLDUPLEX -DESP_LWIP_IP4_REASSEMBLY_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_DNS_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_DHCP_FINE_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_IGMP_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_MLD6_TIMERS_ONDEMAND=ESP_LWIP -DESP_DNS=ESP_LWIP -DESP_LWIP_ARP=ESP_LWIP"
+        export CFLAGS="-DESP_LWIP=LWIP_NETCONN_FULLDUPLEX -DESP_LWIP_IP4_REASSEMBLY_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_DNS_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_DHCP_FINE_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_IGMP_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_MLD6_TIMERS_ONDEMAND=ESP_LWIP -DESP_DNS=ESP_LWIP -DESP_LWIP_ARP=ESP_LWIP"
         export LWIPDIR=../../../../src/
         make TESTFLAGS="-Wno-documentation" -j 4
         chmod +x iteropts.sh && ./iteropts.sh
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index d908ee84..87149f6a 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -86,7 +86,7 @@ validate_opts:
     - *get_contrib
     - cp ${CONTRIB}/examples/example_app/lwipcfg.h.example ${CONTRIB}/examples/example_app/lwipcfg.h
     - cd ${CONTRIB}/ports/unix/example_app
-    - export CFLAGS="-DESP_LWIP=LWIP_NETCONN_FULLDUPLEX -DESP_LWIP_IP4_REASSEMBLY_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_DNS_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_DHCP_FINE_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_IGMP_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_MLD6_TIMERS_ONDEMAND=ESP_LWIP -DESP_DNS=ESP_LWIP"
+    - export CFLAGS="-DESP_LWIP=LWIP_NETCONN_FULLDUPLEX -DESP_LWIP_IP4_REASSEMBLY_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_DNS_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_DHCP_FINE_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_IGMP_TIMERS_ONDEMAND=ESP_LWIP -DESP_LWIP_MLD6_TIMERS_ONDEMAND=ESP_LWIP -DESP_DNS=ESP_LWIP"
     - export LWIPDIR=../../../../src/
     - chmod +x iteropts.sh && ./iteropts.sh
 
diff --git a/src/core/ipv6/ip6_frag.c b/src/core/ipv6/ip6_frag.c
index 8b352f56..5a7a0ae9 100644
--- a/src/core/ipv6/ip6_frag.c
+++ b/src/core/ipv6/ip6_frag.c
@@ -54,6 +54,11 @@
 
 #if LWIP_IPV6 && LWIP_IPV6_REASS  /* don't build if not configured for use in lwipopts.h */
 
+#if ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND
+#include "stdbool.h"
+#include "lwip/timeouts.h"
+static bool s_is_tmr_start = false;
+#endif /* ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND */
 
 /** Setting this to 0, you can turn off checking the fragments for overlapping
  * regions. The code gets a little smaller. Only use this if you know that
@@ -109,10 +114,24 @@ static void ip6_reass_free_complete_datagram(struct ip6_reassdata *ipr);
 static void ip6_reass_remove_oldest_datagram(struct ip6_reassdata *ipr, int pbufs_needed);
 #endif /* IP_REASS_FREE_OLDEST */
 
+#if ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND
+/**
+ * Wrapper function with matching prototype which calls the actual callback
+ */
+static void ip6_reass_timeout_cb(void *arg)
+{
+  LWIP_UNUSED_ARG(arg);
+  ip6_reass_tmr();
+}
+#endif /* ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND */
+
 void
 ip6_reass_tmr(void)
 {
   struct ip6_reassdata *r, *tmp;
+#if ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND
+  bool tmr_restart = false;
+#endif /* ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND */
 
 #if !IPV6_FRAG_COPYHEADER
   LWIP_ASSERT("sizeof(struct ip6_reass_helper) <= IP6_FRAG_HLEN, set IPV6_FRAG_COPYHEADER to 1",
@@ -126,6 +145,9 @@ ip6_reass_tmr(void)
     if (r->timer > 0) {
       r->timer--;
       r = r->next;
+#if ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND
+      tmr_restart = true;
+#endif /* ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND */
     } else {
       /* reassembly timed out */
       tmp = r;
@@ -135,6 +157,14 @@ ip6_reass_tmr(void)
       ip6_reass_free_complete_datagram(tmp);
      }
    }
+#if ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND
+  if (tmr_restart) {
+    sys_timeout(IP6_REASS_TMR_INTERVAL, ip6_reass_timeout_cb, NULL);
+  } else {
+    sys_untimeout(ip6_reass_timeout_cb, NULL);
+    s_is_tmr_start = false;
+  }
+#endif/* ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND */
 }
 
 /**
@@ -357,7 +387,6 @@ ip6_reass(struct pbuf *p)
     /* enqueue the new structure to the front of the list */
     ipr->next = reassdatagrams;
     reassdatagrams = ipr;
-
     /* Use the current IPv6 header for src/dest address reference.
      * Eventually, we will replace it when we get the first fragment
      * (it might be this one, in any case, it is done later). */
@@ -660,6 +689,12 @@ ip6_reass(struct pbuf *p)
     /* Return the pbuf chain */
     return p;
   }
+#if ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND
+  if (!s_is_tmr_start) {
+    sys_timeout(IP6_REASS_TMR_INTERVAL, ip6_reass_timeout_cb, NULL);
+    s_is_tmr_start = true;
+  }
+#endif /* ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND */
   /* the datagram is not (yet?) reassembled completely */
   return NULL;
 
diff --git a/src/core/timeouts.c b/src/core/timeouts.c
index d10a12cd..448159c9 100644
--- a/src/core/timeouts.c
+++ b/src/core/timeouts.c
@@ -105,7 +105,7 @@ const struct lwip_cyclic_timer lwip_cyclic_timers[] = {
 #endif /* LWIP_DNS */
 #if LWIP_IPV6
   {ND6_TMR_INTERVAL, HANDLER(nd6_tmr)},
-#if LWIP_IPV6_REASS
+#if LWIP_IPV6_REASS && !ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND
   {IP6_REASS_TMR_INTERVAL, HANDLER(ip6_reass_tmr)},
 #endif /* LWIP_IPV6_REASS */
 #if LWIP_IPV6_MLD && !ESP_LWIP_MLD6_TIMERS_ONDEMAND
diff --git a/test/apps/lwipopts.h b/test/apps/lwipopts.h
index 37d822ba..19be675f 100644
--- a/test/apps/lwipopts.h
+++ b/test/apps/lwipopts.h
@@ -38,6 +38,7 @@
 
 #define LWIP_IPV4                  1
 #define LWIP_IPV6                  0
+#define LWIP_IPV6_REASS            0
 
 #define NO_SYS                     0
 #define LWIP_SOCKET                (NO_SYS==0)
@@ -300,6 +301,9 @@ void sys_thread_sem_deinit(void);
 #if IP_REASSEMBLY
 #define ESP_LWIP_IP4_REASSEMBLY_TIMERS_ONDEMAND 1
 #endif /* IP_REASSEMBLY */
+#if LWIP_IPV6_REASS
+#define ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND 1
+#endif /* LWIP_IPV6_REASS */
 #define ESP_DNS 1
 #define ESP_LWIP_ARP 1
 #define LWIP_AUTOIP_MAX_CONFLICTS        10
diff --git a/test/unit/lwipopts.h b/test/unit/lwipopts.h
index 3ccb4314..e220318c 100644
--- a/test/unit/lwipopts.h
+++ b/test/unit/lwipopts.h
@@ -163,6 +163,7 @@ u32_t esp_random(void);
 #define ESP_LWIP_DHCP_FINE_TIMERS_ONDEMAND      1
 #define ESP_LWIP_DNS_TIMERS_ONDEMAND            1
 #define ESP_LWIP_IP4_REASSEMBLY_TIMERS_ONDEMAND 1
+#define ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND 1
 
 #else
 #define ESP_LWIP                                0
@@ -182,6 +183,10 @@ u32_t esp_random(void);
 #define ESP_LWIP_IP4_REASSEMBLY_TIMERS_ONDEMAND 0
 #endif /* ESP_LWIP_IP4_REASSEMBLY_TIMERS_ONDEMAND */
 
+#ifndef ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND
+#define ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND 0
+#endif /* ESP_LWIP_IP6_REASSEMBLY_TIMERS_ONDEMAND */
+
 #endif /* ESP_LWIP */
 
 #endif /* LWIP_HDR_LWIPOPTS_H */