diff --git a/requirements/ci.txt b/requirements/ci.txt
index 33c6a89bd..d1b95e469 100644
--- a/requirements/ci.txt
+++ b/requirements/ci.txt
@@ -10,5 +10,5 @@ sphinxcontrib-newsfeed==0.1.4
 pytest-cov==2.5.1
 pygments==2.2.0
 psutil==5.2.2
-mypy==0.520
+mypy==0.520; python_version>="3.5" or platform_system!="Windows"  # It's does not support Python<3.5 under Windows 
 -e .