diff --git a/src/routing_layer/nat_detection.c b/src/routing_layer/nat_detection.c
index 1bbddbe4..81c5632c 100644
--- a/src/routing_layer/nat_detection.c
+++ b/src/routing_layer/nat_detection.c
@@ -1204,6 +1204,9 @@ static uint64_t candidate_fingerprint(struct nat_socket *state, int ready) {
             group_total += hash;
         }
         if (ready || (candidates >= 2 && observers)) total += group_total;
+        if (!ready) DEBUG_DEBUG(DEBUG_CATEGORY_NAT, "NAT cold group candidates node=%016llx socket=%s group=%016llx candidates=%u observers=%u",
+                                (unsigned long long)detector->instance->node_id, state->socket->name,
+                                (unsigned long long)group->group_id, candidates, observers);
     }
     return total;
 }
@@ -1221,6 +1224,9 @@ uint64_t nat_detection_probe_delay(struct NAT_DETECTION *detector) {
             if (!state) continue;
             uint64_t fingerprint = candidate_fingerprint(state, 0);
             if (fingerprint != state->reservation_fingerprint) {
+                DEBUG_DEBUG(DEBUG_CATEGORY_NAT, "NAT cold reservation node=%016llx socket=%s previous=%016llx current=%016llx",
+                            (unsigned long long)detector->instance->node_id, socket->name,
+                            (unsigned long long)state->reservation_fingerprint, (unsigned long long)fingerprint);
                 state->reservation_fingerprint = fingerprint;
                 if (fingerprint) state->cold_until = now + NAT_ROUND_TB + 2500;
             }
diff --git a/tests/test_nat_detection.c b/tests/test_nat_detection.c
index 3b3bf2e9..db430a6a 100644
--- a/tests/test_nat_detection.c
+++ b/tests/test_nat_detection.c
@@ -111,6 +111,7 @@ static void test_all_groups_tcp(void) {
 
 int main(void) {
     debug_config_init(); debug_set_level(DEBUG_LEVEL_WARN); debug_set_category_level(DEBUG_CATEGORY_NAT, DEBUG_LEVEL_DEBUG);
+    if (getenv("UTUN_TEST_DEBUG")) debug_set_category_level(DEBUG_CATEGORY_BGP, DEBUG_LEVEL_DEBUG);
     struct nat_fixture fixture; nat_fixture_init(&fixture);
     struct SC_MYKEYS first, second;
     assert(sc_generate_keypair(&first) == SC_OK && sc_generate_keypair(&second) == SC_OK);