diff --git a/src/eval.c b/src/eval.c
index d12708e..be3f462 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1291,7 +1291,7 @@
 	else
 	{
 	    if (lp->ll_type != NULL
-			      && check_typval_type(lp->ll_type, rettv) == FAIL)
+			   && check_typval_type(lp->ll_type, rettv, 0) == FAIL)
 		return;
 	    set_var_const(lp->ll_name, lp->ll_type, rettv, copy, flags);
 	}
diff --git a/src/proto/vim9type.pro b/src/proto/vim9type.pro
index 5ad87e8..1ac3727 100644
--- a/src/proto/vim9type.pro
+++ b/src/proto/vim9type.pro
@@ -7,10 +7,10 @@
 int func_type_add_arg_types(type_T *functype, int argcount, garray_T *type_gap);
 type_T *typval2type(typval_T *tv, garray_T *type_gap);
 type_T *typval2type_vimvar(typval_T *tv, garray_T *type_gap);
-int check_typval_type(type_T *expected, typval_T *actual_tv);
+int check_typval_type(type_T *expected, typval_T *actual_tv, int argidx);
 void type_mismatch(type_T *expected, type_T *actual);
 void arg_type_mismatch(type_T *expected, type_T *actual, int argidx);
-int check_type(type_T *expected, type_T *actual, int give_msg);
+int check_type(type_T *expected, type_T *actual, int give_msg, int argidx);
 char_u *skip_type(char_u *start, int optional);
 type_T *parse_type(char_u **arg, garray_T *type_gap);
 void common_type(type_T *type1, type_T *type2, type_T **dest, garray_T *type_gap);
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 0d27f2d..282d8dc 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -231,7 +231,7 @@
     enddef
     Func([])
   END
-  call CheckScriptFailure(lines, 'E1012: type mismatch, expected string but got list<unknown>', 5)
+  call CheckScriptFailure(lines, 'E1013: argument 1: type mismatch, expected string but got list<unknown>', 5)
 enddef
 
 " Default arg and varargs
@@ -278,7 +278,7 @@
       enddef
       Func(1, 2, 3)
   END
-  CheckScriptFailure(lines, 'E1012:')
+  CheckScriptFailure(lines, 'E1013: argument 1: type mismatch')
 
   lines =<< trim END
       vim9script
@@ -287,7 +287,7 @@
       enddef
       Func('a', 9)
   END
-  CheckScriptFailure(lines, 'E1012:')
+  CheckScriptFailure(lines, 'E1013: argument 2: type mismatch')
 
   lines =<< trim END
       vim9script
@@ -296,7 +296,7 @@
       enddef
       Func(1, 'a')
   END
-  CheckScriptFailure(lines, 'E1012:')
+  CheckScriptFailure(lines, 'E1013: argument 1: type mismatch')
 enddef
 
 def Test_call_call()
@@ -691,7 +691,7 @@
     enddef
     MyFunc(1234)
   END
-  CheckScriptFailure(lines, 'E1012: type mismatch, expected string but got number')
+  CheckScriptFailure(lines, 'E1013: argument 1: type mismatch, expected string but got number')
 enddef
 
 def Test_vim9script_call_fail_const()
diff --git a/src/version.c b/src/version.c
index 8e11299..901f540 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1551,
+/**/
     1550,
 /**/
     1549,
diff --git a/src/vim9compile.c b/src/vim9compile.c
index bec6988..0c9f56f 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -729,7 +729,7 @@
 	cctx_T	*cctx,
 	int	silent)
 {
-    if (check_type(expected, actual, FALSE) == OK)
+    if (check_type(expected, actual, FALSE, 0) == OK)
 	return OK;
     if (actual->tt_type != VAR_ANY
 	    && actual->tt_type != VAR_UNKNOWN
@@ -3581,7 +3581,7 @@
 
 	generate_ppconst(cctx, ppconst);
 	actual = ((type_T **)stack->ga_data)[stack->ga_len - 1];
-	if (check_type(want_type, actual, FALSE) == FAIL)
+	if (check_type(want_type, actual, FALSE, 0) == FAIL)
 	{
 	    if (need_type(actual, want_type, -1, cctx, FALSE) == FAIL)
 		return FAIL;
@@ -6500,13 +6500,9 @@
 		did_set_arg_type = TRUE;
 		ufunc->uf_arg_types[arg_idx] = val_type;
 	    }
-	    else if (check_type(ufunc->uf_arg_types[arg_idx], val_type, FALSE)
-								       == FAIL)
-	    {
-		arg_type_mismatch(ufunc->uf_arg_types[arg_idx], val_type,
-								  arg_idx + 1);
+	    else if (check_type(ufunc->uf_arg_types[arg_idx], val_type,
+						    TRUE, arg_idx + 1) == FAIL)
 		goto erret;
-	    }
 
 	    if (generate_STORE(&cctx, ISN_STORE, i - count - off, NULL) == FAIL)
 		goto erret;
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 9bc0d45..7a2b21d 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -792,8 +792,8 @@
     for (idx = 0; idx < argc; ++idx)
     {
 	if (ufunc->uf_arg_types != NULL && idx < ufunc->uf_args.ga_len
-		&& check_typval_type(ufunc->uf_arg_types[idx], &argv[idx])
-								       == FAIL)
+		&& check_typval_type(ufunc->uf_arg_types[idx], &argv[idx],
+							      idx + 1) == FAIL)
 	    goto failed_early;
 	copy_tv(&argv[idx], STACK_TV_BOT(0));
 	++ectx.ec_stack.ga_len;
@@ -822,7 +822,8 @@
 
 	    for (idx = 0; idx < vararg_count; ++idx)
 	    {
-		if (check_typval_type(expected, &li->li_tv) == FAIL)
+		if (check_typval_type(expected, &li->li_tv,
+						       argc + idx + 1) == FAIL)
 		    goto failed_early;
 		li = li->li_next;
 	    }
diff --git a/src/vim9script.c b/src/vim9script.c
index e86150a..ed1d6da 100644
--- a/src/vim9script.c
+++ b/src/vim9script.c
@@ -580,7 +580,7 @@
 		semsg(_(e_readonlyvar), name);
 		return FAIL;
 	    }
-	    return check_typval_type(sv->sv_type, value);
+	    return check_typval_type(sv->sv_type, value, 0);
 	}
     }
     iemsg("check_script_var_type(): not found");
diff --git a/src/vim9type.c b/src/vim9type.c
index 07a087b..29466d0 100644
--- a/src/vim9type.c
+++ b/src/vim9type.c
@@ -304,7 +304,7 @@
  * Return FAIL if "expected" and "actual" don't match.
  */
     int
-check_typval_type(type_T *expected, typval_T *actual_tv)
+check_typval_type(type_T *expected, typval_T *actual_tv, int argidx)
 {
     garray_T	type_list;
     type_T	*actual_type;
@@ -313,7 +313,7 @@
     ga_init2(&type_list, sizeof(type_T *), 10);
     actual_type = typval2type(actual_tv, &type_list);
     if (actual_type != NULL)
-	res = check_type(expected, actual_type, TRUE);
+	res = check_type(expected, actual_type, TRUE, argidx);
     clear_type_list(&type_list);
     return res;
 }
@@ -321,22 +321,22 @@
     void
 type_mismatch(type_T *expected, type_T *actual)
 {
-    char *tofree1, *tofree2;
-
-    semsg(_(e_type_mismatch_expected_str_but_got_str),
-		   type_name(expected, &tofree1), type_name(actual, &tofree2));
-    vim_free(tofree1);
-    vim_free(tofree2);
+    arg_type_mismatch(expected, actual, 0);
 }
 
     void
 arg_type_mismatch(type_T *expected, type_T *actual, int argidx)
 {
     char *tofree1, *tofree2;
+    char *typename1 = type_name(expected, &tofree1);
+    char *typename2 = type_name(actual, &tofree2);
 
-    semsg(_(e_argument_nr_type_mismatch_expected_str_but_got_str),
-	    argidx,
-	    type_name(expected, &tofree1), type_name(actual, &tofree2));
+    if (argidx > 0)
+	semsg(_(e_argument_nr_type_mismatch_expected_str_but_got_str),
+						 argidx, typename1, typename2);
+    else
+	semsg(_(e_type_mismatch_expected_str_but_got_str),
+							 typename1, typename2);
     vim_free(tofree1);
     vim_free(tofree2);
 }
@@ -344,9 +344,10 @@
 /*
  * Check if the expected and actual types match.
  * Does not allow for assigning "any" to a specific type.
+ * When "argidx" > 0 it is included in the error message.
  */
     int
-check_type(type_T *expected, type_T *actual, int give_msg)
+check_type(type_T *expected, type_T *actual, int give_msg, int argidx)
 {
     int ret = OK;
 
@@ -359,19 +360,21 @@
 	if (expected->tt_type != actual->tt_type)
 	{
 	    if (give_msg)
-		type_mismatch(expected, actual);
+		arg_type_mismatch(expected, actual, argidx);
 	    return FAIL;
 	}
 	if (expected->tt_type == VAR_DICT || expected->tt_type == VAR_LIST)
 	{
 	    // "unknown" is used for an empty list or dict
 	    if (actual->tt_member != &t_unknown)
-		ret = check_type(expected->tt_member, actual->tt_member, FALSE);
+		ret = check_type(expected->tt_member, actual->tt_member,
+								     FALSE, 0);
 	}
 	else if (expected->tt_type == VAR_FUNC)
 	{
 	    if (expected->tt_member != &t_unknown)
-		ret = check_type(expected->tt_member, actual->tt_member, FALSE);
+		ret = check_type(expected->tt_member, actual->tt_member,
+								     FALSE, 0);
 	    if (ret == OK && expected->tt_argcount != -1
 		    && (actual->tt_argcount < expected->tt_min_argcount
 			|| actual->tt_argcount > expected->tt_argcount))
@@ -383,7 +386,7 @@
 		for (i = 0; i < expected->tt_argcount; ++i)
 		    // Allow for using "any" argument type, lambda's have them.
 		    if (actual->tt_args[i] != &t_any && check_type(
-			       expected->tt_args[i], actual->tt_args[i], FALSE)
+			    expected->tt_args[i], actual->tt_args[i], FALSE, 0)
 								       == FAIL)
 		    {
 			ret = FAIL;
@@ -392,7 +395,7 @@
 	    }
 	}
 	if (ret == FAIL && give_msg)
-	    type_mismatch(expected, actual);
+	    arg_type_mismatch(expected, actual, argidx);
     }
     return ret;
 }