diff --git a/containers/extract-summary/context/main.py b/containers/extract-summary/context/main.py
index cf4ede6..3785887 100644
--- a/containers/extract-summary/context/main.py
+++ b/containers/extract-summary/context/main.py
@@ -22,7 +22,7 @@
     {
         "@type": t.Literal["CellSummary"],
         "annotation_method": str,
-        "cell_source": t.NotRequired[str],
+        "cell_source": t.Optional[str],
         "summary": t.List[CellSummaryRow],
     },
 )