diff --git a/libp2p/pubsub/gossipsub.py b/libp2p/pubsub/gossipsub.py
index 4b5bc251..4bc260be 100644
--- a/libp2p/pubsub/gossipsub.py
+++ b/libp2p/pubsub/gossipsub.py
@@ -10,6 +10,7 @@ from collections.abc import (
 )
 import logging
 import random
+import time
 from typing import (
     Any,
     DefaultDict,
@@ -17,8 +18,6 @@ from typing import (
 
 import trio
 
-import time
-
 from libp2p.abc import (
     IPubsubRouter,
 )
@@ -139,6 +138,7 @@ class GossipSub(IPubsubRouter, Service):
             self.direct_peers[direct_peer.peer_id] = direct_peer
         self.direct_connect_interval = direct_connect_interval
         self.direct_connect_initial_delay = direct_connect_initial_delay
+        self.time_since_last_publish = {}
 
     async def run(self) -> None:
         if self.pubsub is None:
@@ -255,7 +255,7 @@ class GossipSub(IPubsubRouter, Service):
                 logger.debug("Fail to publish message to %s: stream closed", peer_id)
                 self.pubsub._handle_dead_peer(peer_id)
         for topic in pubsub_msg.topicIDs:
-                    self.time_since_last_publish[topic] = int(time.time())
+            self.time_since_last_publish[topic] = int(time.time())
 
     def _get_peers_to_send(
         self, topic_ids: Iterable[str], msg_forwarder: ID, origin: ID
@@ -518,11 +518,10 @@ class GossipSub(IPubsubRouter, Service):
 
     def fanout_heartbeat(self) -> None:
         # Note: the comments here are the exact pseudocode from the spec
-        for topic in self.fanout:
-            if (
-                topic not in self.pubsub.peer_topics
-                or self.time_since_last_publish.get(topic, 0) + self.time_to_live < int(time.time())
-            ):
+        for topic in list(self.fanout):
+            if topic not in self.pubsub.peer_topics or self.time_since_last_publish.get(
+                topic, 0
+            ) + self.time_to_live < int(time.time()):
                 # Remove topic from fanout
                 del self.fanout[topic]
             else:
diff --git a/tests/core/pubsub/test_gossipsub.py b/tests/core/pubsub/test_gossipsub.py
index 5e681091..8e113fa4 100644
--- a/tests/core/pubsub/test_gossipsub.py
+++ b/tests/core/pubsub/test_gossipsub.py
@@ -22,7 +22,7 @@ from tests.utils.pubsub.utils import (
 @pytest.mark.trio
 async def test_join():
     async with PubsubFactory.create_batch_with_gossipsub(
-        4, degree=4, degree_low=3, degree_high=5
+        4, degree=4, degree_low=3, degree_high=5, time_to_live=2
     ) as pubsubs_gsub:
         gossipsubs = [pubsub.router for pubsub in pubsubs_gsub]
         hosts = [pubsub.host for pubsub in pubsubs_gsub]
@@ -49,12 +49,18 @@ async def test_join():
         # is added to central node's fanout
         # publish from the randomly chosen host
         await pubsubs_gsub[central_node_index].publish(topic, b"data")
-
+        await trio.sleep(1)
         # Check that the gossipsub of central node has fanout for the topic
         assert topic in gossipsubs[central_node_index].fanout
         # Check that the gossipsub of central node does not have a mesh for the topic
         assert topic not in gossipsubs[central_node_index].mesh
+        # Check that the gossipsub of central node
+        # has a time_since_last_publish for the topic
+        assert topic in gossipsubs[central_node_index].time_since_last_publish
 
+        await trio.sleep(2)
+        # Check that after ttl the topic is no more in fanout of central node
+        assert topic not in gossipsubs[central_node_index].fanout
         # Central node subscribes the topic
         await pubsubs_gsub[central_node_index].subscribe(topic)