diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9f466d6f..70853bbd 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -43,6 +43,9 @@ jobs:
             cxxstd: "03,11,14,17,2a"
             os: ubuntu-18.04
             install: g++-8
+          - toolset: gcc-9
+            cxxstd: "03,11,14,17,2a"
+            os: ubuntu-18.04
           - toolset: gcc-9
             cxxstd: "03,11,14,17,2a"
             os: ubuntu-20.04