diff --git a/README.md b/README.md
index 4ae9fec..5e2f884 100644
--- a/README.md
+++ b/README.md
@@ -47,7 +47,7 @@ The official documentation is hosted on Read the Docs: [https://brainunit.readth
 - [``pinnx``](https://github.com/chaobrain/pinnx): Physics-Informed Neural Networks for Scientific Machine Learning in JAX.
 
 - [``diffrax``](https://github.com/chaobrain/diffrax): Numerical differential equation solvers in JAX.
-- [``jax-md``](○https://github.com/Routhleck/jax-md): Differentiable Molecular Dynamics in JAX
+- [``jax-md``](https://github.com/Routhleck/jax-md): Differentiable Molecular Dynamics in JAX
 - [``Catalax``](https://github.com/Routhleck/Catalax): JAX-based framework to model biological systems
 - ...
 
diff --git a/brainunit/fft/_fft_change_unit.py b/brainunit/fft/_fft_change_unit.py
index 467a010..ba9c6d7 100644
--- a/brainunit/fft/_fft_change_unit.py
+++ b/brainunit/fft/_fft_change_unit.py
@@ -14,6 +14,7 @@
 # ==============================================================================
 from __future__ import annotations
 
+import sys
 from typing import Callable, Union, Sequence
 
 import jax
@@ -1100,7 +1101,7 @@ def fftfreq(
             freq_unit = Unit.create(get_or_create_dimension(s=-1),
                                     name=f'10^{freq_unit_scale} hertz',
                                     dispname=f'10^{freq_unit_scale} Hz',
-                                    scale=freq_unit_scale,)
+                                    scale=freq_unit_scale, )
         if sys.version_info >= (3, 10):
             return Quantity(jnpfft.fftfreq(n, d.to_decimal(time_unit), dtype=dtype, device=device), unit=freq_unit)
         else: