diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0f568477..d40bebc5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -50,7 +50,6 @@ jobs:
           - 2.4
           - 2.3
           - 2.2
-          - 2.1.9
         env:
           -
             DIFF_LCS_VERSION: "> 1.4.3"
@@ -69,6 +68,8 @@ jobs:
             name_extra: "with diff-lcs 1.4.3"
             env:
               DIFF_LCS_VERSION: "1.4.3"
+          - ruby: 2.1.9
+            bundler: 1
       fail-fast: false
     continue-on-error: ${{ matrix.allow_failure || endsWith(matrix.ruby, 'head') }}
     env: ${{ matrix.env }}