diff --git a/src/channel.c b/src/channel.c
index bdb59f0..fa329bd 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -4883,6 +4883,11 @@
     // Don't open a file in restricted mode.
     if (check_restricted() || check_secure())
 	return;
+    if (in_vim9script()
+	    && (check_for_string_arg(argvars, 0) == FAIL
+		|| check_for_string_arg(argvars, 1) == FAIL))
+	return;
+
     fname = tv_get_string(&argvars[0]);
     if (argvars[1].v_type == VAR_STRING)
 	opt = tv_get_string_buf(&argvars[1], buf);
diff --git a/src/eval.c b/src/eval.c
index 6522f0f..f5fd3e0 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -5298,6 +5298,9 @@
 	return &pos;
     }
 
+    if (in_vim9script() && check_for_string_arg(varp, 0) == FAIL)
+	return NULL;
+
     name = tv_get_string_chk(varp);
     if (name == NULL)
 	return NULL;
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 6d845c1..f83559d 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -2521,6 +2521,8 @@
     static void
 f_char2nr(typval_T *argvars, typval_T *rettv)
 {
+    if (in_vim9script() && check_for_string_arg(argvars, 0) == FAIL)
+	return;
     if (has_mbyte)
     {
 	int	utf8 = 0;
@@ -2685,11 +2687,16 @@
     char_u	*typestr;
     int		error = FALSE;
 
+    if (in_vim9script() && check_for_string_arg(argvars, 0) == FAIL)
+	return;
+
     message = tv_get_string_chk(&argvars[0]);
     if (message == NULL)
 	error = TRUE;
     if (argvars[1].v_type != VAR_UNKNOWN)
     {
+	if (in_vim9script() && check_for_string_arg(argvars, 1) == FAIL)
+	    return;
 	buttons = tv_get_string_buf_chk(&argvars[1], buf);
 	if (buttons == NULL)
 	    error = TRUE;
@@ -2698,6 +2705,8 @@
 	    def = (int)tv_get_number_chk(&argvars[2], &error);
 	    if (argvars[3].v_type != VAR_UNKNOWN)
 	    {
+		if (in_vim9script() && check_for_string_arg(argvars, 3) == FAIL)
+		    return;
 		typestr = tv_get_string_buf_chk(&argvars[3], buf2);
 		if (typestr == NULL)
 		    error = TRUE;
diff --git a/src/filepath.c b/src/filepath.c
index 75662b4..e81eeb1 100644
--- a/src/filepath.c
+++ b/src/filepath.c
@@ -788,9 +788,13 @@
     rettv->vval.v_string = NULL;
 
     if (argvars[0].v_type != VAR_STRING)
+    {
 	// Returning an empty string means it failed.
 	// No error message, for historic reasons.
+	if (in_vim9script())
+	    (void) check_for_string_arg(argvars, 0);
 	return;
+    }
 
     // Return the current directory
     cwd = alloc(MAXPATHL);
diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index 7897db0..eba5ff6 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -204,14 +204,41 @@
   l->assert_equal([1, 2, 3])
 enddef
 
+def Test_ch_logfile()
+  assert_fails('ch_logfile(true)', 'E1174')
+  assert_fails('ch_logfile("foo", true)', 'E1174')
+enddef
+
 def Test_char2nr()
   char2nr('あ', true)->assert_equal(12354)
+
+  assert_fails('char2nr(true)', 'E1174')
+enddef
+
+def Test_charclass()
+  assert_fails('charclass(true)', 'E1174')
+enddef
+
+def Test_chdir()
+  assert_fails('chdir(true)', 'E1174')
 enddef
 
 def Test_col()
   new
   setline(1, 'asdf')
   col([1, '$'])->assert_equal(5)
+
+  assert_fails('col(true)', 'E1174')
+enddef
+
+def Test_confirm()
+  if !has('dialog_con') && !has('dialog_gui')
+    CheckFeature dialog_con
+  endif
+
+  assert_fails('call confirm(true)', 'E1174')
+  assert_fails('call confirm("yes", true)', 'E1174')
+  assert_fails('call confirm("yes", "maybe", 2, true)', 'E1174')
 enddef
 
 def Test_copy_return_type()
@@ -675,6 +702,10 @@
   var->assert_equal(['a', 'b'])
 enddef
 
+def Test_line()
+  assert_fails('line(true)', 'E1174')
+enddef
+
 def Test_list2str_str2list_utf8()
   var s = "\u3042\u3044"
   var l = [0x3042, 0x3044]
diff --git a/src/version.c b/src/version.c
index 8e04e9a..da9073c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2666,
+/**/
     2665,
 /**/
     2664,