diff --git a/slixmpp_omemo/__init__.py b/slixmpp_omemo/__init__.py
index b885d8b..f35440d 100644
--- a/slixmpp_omemo/__init__.py
+++ b/slixmpp_omemo/__init__.py
@@ -536,8 +536,8 @@ class XEP_0384(BasePlugin):
             if session is None:
                 continue
             skr = session._DoubleRatchet__skr
-            sending = skr.sending_chain_length or -1
-            receiving = skr.receiving_chain_length or -1
+            sending = skr.sending_chain_length or 0
+            receiving = skr.receiving_chain_length or 0
             lengths['sending'].append((did, sending))
             lengths['receiving'].append((did, receiving))
 
@@ -556,8 +556,7 @@ class XEP_0384(BasePlugin):
 
         receiving_chain_lengths = self._chain_lengths(jid).get('receiving', [])
         lengths = map(lambda d_l: d_l[1], receiving_chain_lengths)
-        min_length = reduce(lambda x, d_l: min(x, d_l[1]), receiving_chain_lengths, 0) == -1
-        return min_length == -1 or max(lengths, default=0) > self.heartbeat_after
+        return max(lengths, default=0) > self.heartbeat_after
 
     async def make_heartbeat(self, jid: JID) -> Message:
         """