diff --git a/.github/workflows/python-package.yml b/.github/workflows/python-package.yml
index 98234be..268fa0a 100644
--- a/.github/workflows/python-package.yml
+++ b/.github/workflows/python-package.yml
@@ -18,7 +18,7 @@ on:
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     strategy:
       matrix:
         python-version: [2.7, 3.4, 3.5, 3.6, 3.7, 3.8]
diff --git a/setup.py b/setup.py
index fdd2d48..f0f2100 100644
--- a/setup.py
+++ b/setup.py
@@ -26,6 +26,6 @@
     'Mailing List': 'https://www.freelists.org/list/psychrnn',
     },
 
-    install_requires=['python_version>="2.7",!="3.0*",!="3.1*",!="3.2*",!="3.3*"', 'tensorflow']
+    install_requires=['python_version>="2.7",!="3.0*",!="3.1*",!="3.2*",!="3.3*"', 'tensorflow >= 1.13.1', 'numpy']
 
-)
\ No newline at end of file
+)