diff --git a/src/meshcore/commands.py b/src/meshcore/commands.py
index d49e8ec..7e055bb 100644
--- a/src/meshcore/commands.py
+++ b/src/meshcore/commands.py
@@ -253,9 +253,12 @@ class CommandHandler:
         return await self.send(b"\x25" \
                 + int(pin).to_bytes(4, 'little'), [EventType.OK, EventType.ERROR])
                 
-    async def get_contacts(self) -> Event:
+    async def get_contacts(self, lastmod=0) -> Event:
         logger.debug("Getting contacts")
-        return await self.send(b"\x04", [EventType.CONTACTS, EventType.ERROR])
+        data=b"\x04"
+        if lastmod > 0:
+            data = data + lastmod.to_bytes(4, 'little')
+        return await self.send(data, [EventType.CONTACTS, EventType.ERROR])
         
     async def reset_path(self, key: DestinationType) -> Event:
         key_bytes = _validate_destination(key, prefix_length=32)
diff --git a/src/meshcore/meshcore.py b/src/meshcore/meshcore.py
index 108da2b..6a37829 100644
--- a/src/meshcore/meshcore.py
+++ b/src/meshcore/meshcore.py
@@ -47,6 +47,7 @@ class MeshCore:
         self._pending_contacts = {}
         self._self_info = {}
         self._time = 0
+        self._lastmod = 0
         
         # Set up event subscriptions to track data
         self._setup_data_tracking()
@@ -179,7 +180,9 @@ class MeshCore:
     def _setup_data_tracking(self):
         """Set up event subscriptions to track data internally"""
         async def _update_contacts(event):
-            self._contacts = event.payload
+            self._contacts.update(event.payload)
+            if "lastmod" in event.attributes :
+                self._lastmod = event.attributes['lastmod']
             self._contacts_dirty = False
             
         async def _add_pending_contact(event):
@@ -353,6 +356,6 @@ class MeshCore:
     async def ensure_contacts(self, follow=False):
         """Ensure contacts are fetched"""
         if not self._contacts or (follow and self._contacts_dirty) :
-            await self.commands.get_contacts()
+            await self.commands.get_contacts(lastmod = self._lastmod)
             return True
         return False
diff --git a/src/meshcore/reader.py b/src/meshcore/reader.py
index 4b8a190..aefcce7 100644
--- a/src/meshcore/reader.py
+++ b/src/meshcore/reader.py
@@ -68,7 +68,11 @@ class MessageReader:
                 self.contacts[c["public_key"]] = c
             
         elif packet_type_value == PacketType.CONTACT_END.value:
-            await self.dispatcher.dispatch(Event(EventType.CONTACTS, self.contacts))
+            lastmod = int.from_bytes(data[1:5], byteorder='little')
+            attributes = {
+                "lastmod": lastmod,
+            }
+            await self.dispatcher.dispatch(Event(EventType.CONTACTS, self.contacts, attributes))
             
         elif packet_type_value == PacketType.SELF_INFO.value:
             self_info = {}