diff --git a/requirements-dev.txt b/requirements-dev.txt
index 16ae072..9c46b21 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -4,7 +4,7 @@ flake8-commas==2.0.0
 flake8-comprehensions==2.1.0
 flake8-docstrings==1.3.0
 flake8-per-file-ignores==0.8.1
-isort==4.3.20
+isort==4.3.21
 pep8-naming==0.8.2
 pypi-version==0.2.0
 radon==3.0.3