diff --git a/devchat/assistant.py b/devchat/assistant.py
index af1f0942..651365e3 100644
--- a/devchat/assistant.py
+++ b/devchat/assistant.py
@@ -110,6 +110,8 @@ def iterate_response(self) -> Iterator[str]:
                     first_chunk = False
                     yield self._prompt.formatted_header()
                 yield delta
+            if not self._prompt.responses or len(self._prompt.responses) == 0:
+                raise RuntimeError("No responses returned from the chat API")
             self._store.store_prompt(self._prompt)
             yield self._prompt.formatted_footer(0) + '\n'
             for index in range(1, len(self._prompt.responses)):
@@ -117,6 +119,8 @@ def iterate_response(self) -> Iterator[str]:
         else:
             response_str = self._chat.complete_response(self._prompt)
             self._prompt.set_response(response_str)
+            if not self._prompt.responses or len(self._prompt.responses) == 0:
+                raise RuntimeError("No responses returned from the chat API")
             self._store.store_prompt(self._prompt)
             for index in range(len(self._prompt.responses)):
                 yield self._prompt.formatted_full_response(index) + '\n'
diff --git a/devchat/store.py b/devchat/store.py
index 47c81d9a..22804a0c 100644
--- a/devchat/store.py
+++ b/devchat/store.py
@@ -92,7 +92,7 @@ def _update_topics_table(self, prompt: Prompt):
                     logger.warning("Topic %s not found in graph but added", topic['root'])
                 if prompt.parent == topic['root'] or \
                         prompt.parent in nx.ancestors(self._graph, topic['root']):
-                    topic['latest_time'] = max(topic['latest_time'], prompt.timestamp)
+                    topic['latest_time'] = prompt.timestamp
                     self._topics_table.update(topic, doc_ids=[topic.doc_id])
                     break
         else: