diff --git a/src/channel.c b/src/channel.c
index c0572d3..5f78777 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -4270,6 +4270,11 @@
     rettv->v_type = VAR_STRING;
     rettv->vval.v_string = NULL;
 
+    if (in_vim9script()
+	    && (check_for_chan_or_job_arg(argvars, 0) == FAIL
+		|| check_for_opt_dict_arg(argvars, 2) == FAIL))
+	return;
+
     channel = get_channel_arg(&argvars[0], TRUE, FALSE, 0);
     if (channel == NULL)
 	return;
@@ -4330,6 +4335,12 @@
     rettv->v_type = VAR_STRING;
     rettv->vval.v_string = NULL;
 
+    if (in_vim9script()
+	    && (check_for_chan_or_job_arg(argvars, 0) == FAIL
+		|| check_for_string_or_blob_arg(argvars, 1) == FAIL
+		|| check_for_opt_dict_arg(argvars, 2) == FAIL))
+	return;
+
     if (argvars[1].v_type == VAR_BLOB)
     {
 	text = argvars[1].vval.v_blob->bv_ga.ga_data;
@@ -4815,9 +4826,16 @@
     void
 f_ch_getbufnr(typval_T *argvars, typval_T *rettv)
 {
-    channel_T *channel = get_channel_arg(&argvars[0], FALSE, FALSE, 0);
+    channel_T *channel;
 
     rettv->vval.v_number = -1;
+
+    if (in_vim9script()
+	    && (check_for_chan_or_job_arg(argvars, 0) == FAIL
+		|| check_for_string_arg(argvars, 1) == FAIL))
+	return;
+
+    channel = get_channel_arg(&argvars[0], FALSE, FALSE, 0);
     if (channel != NULL)
     {
 	char_u	*what = tv_get_string(&argvars[1]);
@@ -4894,6 +4912,7 @@
     // 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))