diff --git a/src/crewai/knowledge/storage/knowledge_storage.py b/src/crewai/knowledge/storage/knowledge_storage.py
index c3b9d7e2b..fad988414 100644
--- a/src/crewai/knowledge/storage/knowledge_storage.py
+++ b/src/crewai/knowledge/storage/knowledge_storage.py
@@ -154,13 +154,15 @@ class KnowledgeStorage(BaseKnowledgeStorage):
                 filtered_ids.append(doc_id)
 
             # If we have no metadata at all, set it to None
-            final_metadata: Optional[List[Dict[str, Union[str, int, float, bool]]]] = (
-                None if all(m is None for m in filtered_metadata) else [
-                    {k: v for k, v in m.items() if isinstance(v, (str, int, float, bool))}
-                    if m is not None else None
-                    for m in filtered_metadata
-                ]
-            )
+            final_metadata: Optional[List[Dict[str, Union[str, int, float, bool]]]] = None
+            if not all(m is None for m in filtered_metadata):
+                final_metadata = []
+                for m in filtered_metadata:
+                    if m is not None:
+                        filtered_m = {k: v for k, v in m.items() if isinstance(v, (str, int, float, bool))}
+                        final_metadata.append(filtered_m)
+                    else:
+                        final_metadata.append({"empty": True})
 
             self.collection.upsert(
                 documents=filtered_docs,