diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index e1ab097..a7343e2 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -2,7 +2,7 @@ name: build
 on: [push, pull_request]
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         python-version: [3.6, 3.7, 3.8, 3.9]
diff --git a/setup.py b/setup.py
index d8f6781..697333e 100644
--- a/setup.py
+++ b/setup.py
@@ -28,7 +28,7 @@
         "License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)",
         "Operating System :: OS Independent",
     ],
-    python_requires='>=3.6',
+    python_requires=">=3.6",
     install_requires=[
         "numpy>=1.17.0",
         "XeprAPI",