diff --git a/sync.py b/sync.py
index 3572ad4..27e2664 100755
--- a/sync.py
+++ b/sync.py
@@ -61,7 +61,7 @@ def read_gviz(sheet: str) -> list[list[str]]:
     def cell_value(cell: dict | None) -> str:
         if not cell:
             return ""
-        value = cell.get("f", cell.get("v", ""))
+        value = cell.get("f") if cell.get("f") is not None else cell.get("v", "")
         if value is None:
             return ""
         if isinstance(value, bool):