diff --git a/src/userfunc.c b/src/userfunc.c
index b49cef1..04c2641 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -55,6 +55,7 @@
  * Get one function argument.
  * If "argtypes" is not NULL also get the type: "arg: type".
  * If "types_optional" is TRUE a missing type is OK, use "any".
+ * If "evalarg" is not NULL use it to check for an already declared name.
  * Return a pointer to after the type.
  * When something is wrong return "arg".
  */
@@ -64,6 +65,7 @@
 	garray_T    *newargs,
 	garray_T    *argtypes,
 	int	    types_optional,
+	evalarg_T   *evalarg,
 	int	    skip)
 {
     char_u	*p = arg;
@@ -81,13 +83,11 @@
 	return arg;
     }
 
-    // Vim9 script: cannot use script var name for argument.
-    if (!skip && argtypes != NULL && script_var_exists(arg, p - arg,
-							    FALSE, NULL) == OK)
-    {
-	semsg(_(e_variable_already_declared_in_script), arg);
+    // Vim9 script: cannot use script var name for argument. In function: also
+    // check local vars and arguments.
+    if (!skip && argtypes != NULL && check_defined(arg, p - arg,
+		    evalarg == NULL ? NULL : evalarg->eval_cctx, TRUE) == FAIL)
 	return arg;
-    }
 
     if (newargs != NULL && ga_grow(newargs, 1) == FAIL)
 	return arg;
@@ -173,6 +173,7 @@
     garray_T	*newargs,
     garray_T	*argtypes,	// NULL unless using :def
     int		types_optional,	// types optional if "argtypes" is not NULL
+    evalarg_T	*evalarg,	// context or NULL
     int		*varargs,
     garray_T	*default_args,
     int		skip,
@@ -247,7 +248,7 @@
 
 		arg = p;
 		p = one_function_arg(p, newargs, argtypes, types_optional,
-									 skip);
+								evalarg, skip);
 		if (p == arg)
 		    break;
 		if (*skipwhite(p) == '=')
@@ -260,7 +261,8 @@
 	else
 	{
 	    arg = p;
-	    p = one_function_arg(p, newargs, argtypes, types_optional, skip);
+	    p = one_function_arg(p, newargs, argtypes, types_optional,
+								evalarg, skip);
 	    if (p == arg)
 		break;
 
@@ -576,7 +578,7 @@
     // be found after the arguments.
     s = *arg + 1;
     ret = get_function_args(&s, equal_arrow ? ')' : '-', NULL,
-	    types_optional ? &argtypes : NULL, types_optional,
+	    types_optional ? &argtypes : NULL, types_optional, evalarg,
 						 NULL, NULL, TRUE, NULL, NULL);
     if (ret == FAIL || skip_arrow(s, equal_arrow, &ret_type, NULL) == NULL)
     {
@@ -592,7 +594,7 @@
 	pnewargs = NULL;
     *arg += 1;
     ret = get_function_args(arg, equal_arrow ? ')' : '-', pnewargs,
-	    types_optional ? &argtypes : NULL, types_optional,
+	    types_optional ? &argtypes : NULL, types_optional, evalarg,
 					    &varargs, NULL, FALSE, NULL, NULL);
     if (ret == FAIL
 		  || (s = skip_arrow(*arg, equal_arrow, &ret_type,
@@ -683,7 +685,6 @@
 
 	fp->uf_refcount = 1;
 	set_ufunc_name(fp, name);
-	hash_add(&func_hashtab, UF2HIKEY(fp));
 	fp->uf_args = newargs;
 	ga_init(&fp->uf_def_args);
 	if (types_optional)
@@ -726,6 +727,8 @@
 	pt->pt_refcount = 1;
 	rettv->vval.v_partial = pt;
 	rettv->v_type = VAR_PARTIAL;
+
+	hash_add(&func_hashtab, UF2HIKEY(fp));
     }
 
     eval_lavars_used = old_eval_lavars;
@@ -3278,7 +3281,7 @@
     ++p;
     if (get_function_args(&p, ')', &newargs,
 			eap->cmdidx == CMD_def ? &argtypes : NULL, FALSE,
-			 &varargs, &default_args, eap->skip,
+			 NULL, &varargs, &default_args, eap->skip,
 			 eap, &line_to_free) == FAIL)
 	goto errret_2;
     whitep = p;