diff --git a/scripts/csv.py b/scripts/csv.py
index 9b9e7b01..59b443e1 100755
--- a/scripts/csv.py
+++ b/scripts/csv.py
@@ -2619,7 +2619,9 @@ def main(csv_paths, *,
             if v is not None]
     exprs = [(k, v)
             for k, v in it.chain(
-                ((k, v) for (k, v), hidden in (fields or [])),
+                # expr-less fields at least imply typechecking
+                ((k, v) if v is not None else (k, CsvExpr(k))
+                    for (k, v), hidden in (fields or [])),
                 ((k, v) for (k, v), reverse in (sort or [])),
                 ((k, v) for (k, v), reverse in (hot or [])))
             if v is not None]