diff --git a/.github/workflows/unix_linux.yml b/.github/workflows/unix_linux.yml
index 970b1350..020d3a73 100644
--- a/.github/workflows/unix_linux.yml
+++ b/.github/workflows/unix_linux.yml
@@ -24,7 +24,7 @@ jobs:
       matrix:
         cubit: [2021.4, 2021.5]
         os: [ubuntu]
-        os_version: [18.04, 20.04, 21.04]
+        os_version: [20.04, 21.04]
         include:
           - os: ubuntu
             os_version: 18.04