diff --git a/slixmpp_omemo/__init__.py b/slixmpp_omemo/__init__.py
index f35440d..4825db3 100644
--- a/slixmpp_omemo/__init__.py
+++ b/slixmpp_omemo/__init__.py
@@ -543,7 +543,7 @@ class XEP_0384(BasePlugin):
 
         return lengths
 
-    def should_heartbeat(self, jid: JID) -> bool:
+    def should_heartbeat(self, jid: JID, msg: Union[Message, Encrypted]) -> bool:
         """
             Returns whether we should send a heartbeat message for JID.
             See notes about heartbeat in
@@ -554,9 +554,28 @@ class XEP_0384(BasePlugin):
             sessions hasn't been answered in a while.
         """
 
+        new_session: bool = False
+        inactive_session: bool = False
+
+        # Is the message is a prekey message. If so assume it's a new session
+        encrypted = msg
+        if isinstance(msg, Message):
+            encrypted = msg['omemo_encrypted']
+
+        header = encrypted['header']
+        key = header.xml.find("{%s}key[@rid='%s']" % (
+            OMEMO_BASE_NS, self._device_id))
+        if key is not None:
+            key = Key(key)
+            new_session = key['prekey'] in TRUE_VALUES
+
+        # Otherwise find how many message we haven't replied to in all of the
+        # sessions associated to this JID.
         receiving_chain_lengths = self._chain_lengths(jid).get('receiving', [])
         lengths = map(lambda d_l: d_l[1], receiving_chain_lengths)
-        return max(lengths, default=0) > self.heartbeat_after
+        inactive_session = max(lengths, default=0) > self.heartbeat_after
+
+        return new_session or inactive_session
 
     async def make_heartbeat(self, jid: JID) -> Message:
         """
@@ -663,7 +682,7 @@ class XEP_0384(BasePlugin):
         finally:
             asyncio.ensure_future(self._publish_bundle())
 
-        if self.auto_heartbeat and self.should_heartbeat(sender):
+        if self.auto_heartbeat and self.should_heartbeat(sender, encrypted):
             async def send_heartbeat():
                 msg = await self.make_heartbeat(JID(jid))
                 msg.send()