diff --git a/src/charset.c b/src/charset.c
index 79a2815..d26a696 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -943,7 +943,7 @@
 init_chartabsize_arg(
 	chartabsize_T	*cts,
 	win_T		*wp,
-	linenr_T	lnum,
+	linenr_T	lnum UNUSED,
 	colnr_T		col,
 	char_u		*line,
 	char_u		*ptr)