diff --git a/libs/langchain/langchain/retrievers/merger_retriever.py b/libs/langchain/langchain/retrievers/merger_retriever.py
index f5326773bc..4979779c25 100644
--- a/libs/langchain/langchain/retrievers/merger_retriever.py
+++ b/libs/langchain/langchain/retrievers/merger_retriever.py
@@ -80,7 +80,7 @@ class MergerRetriever(BaseRetriever):
 
         # Merge the results of the retrievers.
         merged_documents = []
-        max_docs = max(len(docs) for docs in retriever_docs)
+        max_docs = max(map(len, retriever_docs), default=0)
         for i in range(max_docs):
             for retriever, doc in zip(self.retrievers, retriever_docs):
                 if i < len(doc):
@@ -113,7 +113,7 @@ class MergerRetriever(BaseRetriever):
 
         # Merge the results of the retrievers.
         merged_documents = []
-        max_docs = max(len(docs) for docs in retriever_docs)
+        max_docs = max(map(len, retriever_docs), default=0)
         for i in range(max_docs):
             for retriever, doc in zip(self.retrievers, retriever_docs):
                 if i < len(doc):