diff --git a/.github/workflows/cpp_ubuntu.yml b/.github/workflows/cpp_ubuntu.yml
index 4bd53a090..82c5706d8 100644
--- a/.github/workflows/cpp_ubuntu.yml
+++ b/.github/workflows/cpp_ubuntu.yml
@@ -9,7 +9,7 @@ on:
 jobs:
   build-ubuntu:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     
     steps:
     - uses: actions/checkout@v2