diff --git a/src/digraph.c b/src/digraph.c
index 745cbbb..4a18539 100644
--- a/src/digraph.c
+++ b/src/digraph.c
@@ -2406,6 +2406,10 @@
 
     rettv->v_type = VAR_STRING;
     rettv->vval.v_string = NULL;  // Return empty string for failure
+
+    if (in_vim9script() && check_for_string_arg(argvars, 0) == FAIL)
+	return;
+
     digraphs = tv_get_string_chk(&argvars[0]);
 
     if (digraphs == NULL)
@@ -2439,6 +2443,9 @@
 # ifdef FEAT_DIGRAPHS
     int     flag_list_all;
 
+    if (in_vim9script() && check_for_opt_number_arg(argvars, 0) == FAIL)
+	return;
+
     if (argvars[0].v_type == VAR_UNKNOWN)
 	flag_list_all = FALSE;
     else
@@ -2466,6 +2473,11 @@
     rettv->v_type = VAR_BOOL;
     rettv->vval.v_number = VVAL_FALSE;
 
+    if (in_vim9script()
+	    && (check_for_string_arg(argvars, 0) == FAIL
+		|| check_for_number_arg(argvars, 1) == FAIL))
+	return;
+
     if (!digraph_set_common(&argvars[0], &argvars[1]))
 	return;