diff --git a/src/cindent.c b/src/cindent.c
index ce02402..b751206 100644
--- a/src/cindent.c
+++ b/src/cindent.c
@@ -4129,6 +4129,9 @@
     pos_T	pos;
     linenr_T	lnum;
 
+    if (in_vim9script() && check_for_lnum_arg(argvars, 0) == FAIL)
+	return;
+
     pos = curwin->w_cursor;
     lnum = tv_get_lnum(argvars);
     if (lnum >= 1 && lnum <= curbuf->b_ml.ml_line_count)