diff --git a/timm/models/tiny_vit.py b/timm/models/tiny_vit.py
index 2ce5820f..fc341f9a 100644
--- a/timm/models/tiny_vit.py
+++ b/timm/models/tiny_vit.py
@@ -9,13 +9,14 @@ Adapted from official impl at https://github.com/microsoft/Cream/tree/main/TinyV
 __all__ = ['TinyVit']
 import math
 import itertools
+from typing import Dict
 
 import torch
 import torch.nn as nn
 import torch.nn.functional as F
 
 from timm.data import IMAGENET_DEFAULT_MEAN, IMAGENET_DEFAULT_STD
-from timm.layers import DropPath, to_2tuple, trunc_normal_, resample_relative_position_bias_table
+from timm.layers import DropPath, to_2tuple, trunc_normal_, resample_relative_position_bias_table, _assert
 from ._builder import build_model_with_cfg
 from ._manipulate import checkpoint_seq
 from ._registry import register_model, generate_default_cfgs
@@ -178,6 +179,8 @@ class ClassifierHead(nn.Module):
 
 
 class Attention(torch.nn.Module):
+    attention_bias_cache: Dict[str, torch.Tensor]
+
     def __init__(self, dim, key_dim, num_heads=8, attn_ratio=4, resolution=(14, 14)):
         super().__init__()
         assert isinstance(resolution, tuple) and len(resolution) == 2
@@ -304,7 +307,7 @@ class TinyVitBlock(nn.Module):
     def forward(self, x):
         H, W = self.input_resolution
         B, L, C = x.shape
-        assert L == H * W, "input feature has wrong size"
+        _assert(L == H * W, f"input feature has wrong size, expect {H * W}, got {L}")
         res_x = x
         if H == self.window_size and W == self.window_size:
             x = self.attn(x)