diff --git a/src/typval.c b/src/typval.c
index 4f6e41d..b131ba2 100644
--- a/src/typval.c
+++ b/src/typval.c
@@ -360,6 +360,20 @@
 #endif
 
 /*
+ * Give an error and return FAIL unless "args[idx]" is unknown
+ */
+    int
+check_for_unknown_arg(typval_T *args, int idx)
+{
+    if (args[idx].v_type != VAR_UNKNOWN)
+    {
+	semsg(_(e_too_many_arguments), idx + 1);
+	return FAIL;
+    }
+    return OK;
+}
+
+/*
  * Give an error and return FAIL unless "args[idx]" is a string.
  */
     int