diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index bc42e31bb..ca42d8c3b 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -94,7 +94,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        compiler: ['4.8', '4' '5', '6', '7', '8', '9', '10', '11', '12', 'latest']
+        compiler: ['4.8', '4', '5', '6', '7', '8', '9', '10', '11', '12', 'latest']
     container: gcc:${{ matrix.compiler }}
     steps:
       - uses: actions/checkout@v3