diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9bf05b41..c1f1dbb9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,6 +13,7 @@ jobs:
       matrix:
         version:
           - '1.9'
+          - '1'
         os:
           - ubuntu-latest
           - macOS-latest