diff --git a/libs/langchain/langchain/chains/qa_with_sources/base.py b/libs/langchain/langchain/chains/qa_with_sources/base.py
index e6a07c37630..79b083de0b7 100644
--- a/libs/langchain/langchain/chains/qa_with_sources/base.py
+++ b/libs/langchain/langchain/chains/qa_with_sources/base.py
@@ -120,9 +120,9 @@ class BaseQAWithSourcesChain(Chain, ABC):
 
     def _split_sources(self, answer: str) -> Tuple[str, str]:
         """Split sources from answer."""
-        if re.search(r"SOURCES?[:\s]", answer, re.IGNORECASE):
+        if re.search(r"SOURCES?[:]\s", answer, re.IGNORECASE):
             answer, sources = re.split(
-                r"SOURCES?[:]|QUESTION:\s", answer, flags=re.IGNORECASE
+                r"SOURCES?[:]\s|QUESTION:\s", answer, flags=re.IGNORECASE
             )[:2]
             sources = re.split(r"\n", sources)[0].strip()
         else: