From 8af29c200d504ea977692c1c269915d32f0162b2 Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Mon, 18 Mar 2024 21:35:12 +0100
Subject: [PATCH] strengthen type check

---
 src/lib/format.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/lib/format.pl b/src/lib/format.pl
index 82d96701..2478e371 100644
--- a/src/lib/format.pl
+++ b/src/lib/format.pl
@@ -88,7 +88,7 @@ format_(Fs, Args) -->
         format_cells(Cells).
 
 format_args_cells(Fs, Args, Cells) :-
-        must_be(list, Fs),
+        must_be(chars, Fs),
         must_be(list, Args),
         unique_variable_names(Args, VNs),
         phrase(cells(Fs,Args,0,[],VNs), Cells).
-- 
2.54.0