diff --git a/telethon/tl/custom/conversation.py b/telethon/tl/custom/conversation.py
index e065dca7..79fb6409 100644
--- a/telethon/tl/custom/conversation.py
+++ b/telethon/tl/custom/conversation.py
@@ -369,7 +369,7 @@ class Conversation(ChatGetter):
             del self._pending_reads[to_remove]
 
     def _get_message_id(self, message):
-        if message:
+        if message is not None:  # 0 is valid but false-y, check for None
             return message if isinstance(message, int) else message.id
         elif self._last_outgoing:
             return self._last_outgoing
diff --git a/telethon/version.py b/telethon/version.py
index 43212309..0b047156 100644
--- a/telethon/version.py
+++ b/telethon/version.py
@@ -1,3 +1,3 @@
 # Versions should comply with PEP440.
 # This line is parsed in setup.py:
-__version__ = '1.7.1'
+__version__ = '1.7.2'