diff --git a/brainpy/_src/math/compat_numpy.py b/brainpy/_src/math/compat_numpy.py
index eeb408798..c2c1c4b2f 100644
--- a/brainpy/_src/math/compat_numpy.py
+++ b/brainpy/_src/math/compat_numpy.py
@@ -1,7 +1,5 @@
 # -*- coding: utf-8 -*-
 
-from typing import (Union, Any, Protocol)
-
 import jax.numpy as jnp
 import numpy as np
 from jax.tree_util import tree_flatten, tree_unflatten
@@ -12,13 +10,6 @@
 from .ndarray import Array
 
 
-class SupportsDType(Protocol):
-  @property
-  def dtype(self) -> np.dtype: ...
-
-
-DTypeLike = Union[Any, str, np.dtype, SupportsDType]
-
 __all__ = [
   'full', 'full_like', 'eye', 'identity', 'diag', 'tri', 'tril', 'triu',
   'empty', 'empty_like', 'ones', 'ones_like', 'zeros', 'zeros_like',