diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 67b4802..cb679f8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,7 +8,7 @@ jobs:
     runs-on: ${{ matrix.operating-system }}
     strategy:
       matrix:
-        operating-system: ['ubuntu-18.04']
+        operating-system: ['ubuntu-20.04']
         php-versions: ['5.5', '5.6', '7.0']
         phpunit-versions: ['7.5.20']
     steps: