diff --git a/langchain/chains/chat_vector_db/base.py b/langchain/chains/chat_vector_db/base.py
index c2bbd4df4986d..8948eebd0f962 100644
--- a/langchain/chains/chat_vector_db/base.py
+++ b/langchain/chains/chat_vector_db/base.py
@@ -1,7 +1,7 @@
 """Chain for chatting with a vector database."""
 from __future__ import annotations
 
-from typing import Any, Dict, List, Tuple
+from typing import Any, Dict, List, Tuple, Optional, Union
 
 from pydantic import BaseModel
 
@@ -33,6 +33,7 @@ class ChatVectorDBChain(Chain, BaseModel):
     output_key: str = "answer"
     return_source_documents: bool = False
     top_k_docs_for_context: int = 4
+    search_distance: Optional[Union[float, str]]
     """Return the source documents."""
 
     @property
@@ -90,7 +91,7 @@ def _call(self, inputs: Dict[str, Any]) -> Dict[str, Any]:
         else:
             new_question = question
         docs = self.vectorstore.similarity_search(
-            new_question, k=self.top_k_docs_for_context, **vectordbkwargs
+            new_question, k=self.top_k_docs_for_context, search_distance=self.search_distance, **vectordbkwargs
         )
         new_inputs = inputs.copy()
         new_inputs["question"] = new_question
@@ -113,7 +114,7 @@ async def _acall(self, inputs: Dict[str, Any]) -> Dict[str, str]:
             new_question = question
         # TODO: This blocks the event loop, but it's not clear how to avoid it.
         docs = self.vectorstore.similarity_search(
-            new_question, k=self.top_k_docs_for_context, **vectordbkwargs
+            new_question, k=self.top_k_docs_for_context, search_distance=self.search_distance, **vectordbkwargs
         )
         new_inputs = inputs.copy()
         new_inputs["question"] = new_question
diff --git a/langchain/vectorstores/weaviate.py b/langchain/vectorstores/weaviate.py
index 2ee82e59b838f..ab904a297f93d 100644
--- a/langchain/vectorstores/weaviate.py
+++ b/langchain/vectorstores/weaviate.py
@@ -1,7 +1,7 @@
 """Wrapper around weaviate vector database."""
 from __future__ import annotations
 
-from typing import Any, Iterable, List, Optional
+from typing import Any, Iterable, List, Optional, Dict
 from uuid import uuid4
 
 from langchain.docstore.document import Document
@@ -78,9 +78,9 @@ def similarity_search(
         self, query: str, k: int = 4, **kwargs: Any
     ) -> List[Document]:
         """Look up similar documents in weaviate."""
-        content = {"concepts": [query]}
-        if kwargs.get("certainty") and isinstance(kwargs.get("certainty"), float):
-            content["certainty"] = kwargs.get("certainty")
+        content: Dict[str, Any] = {"concepts": [query]}
+        if kwargs.get("search_distance"):
+            content["certainty"] = kwargs.get("search_distance")
         query_obj = self._client.query.get(self._index_name, self._query_attrs)
         result = query_obj.with_near_text(content).with_limit(k).do()
         docs = []