diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8ebe248f..25e695f9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,7 +13,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-20.04, macos-latest ]
-        smalltalk: [ GemStone64-3.5.3, GemStone64-3.5.8,  GemStone64-3.6.0, GemStone64-3.6.5 ]
+        smalltalk: [ GemStone64-3.5.3, GemStone64-3.5.8,  GemStone64-3.6.0, GemStone64-3.6.6 ]
     runs-on: ${{ matrix.os }}
     name: ${{ matrix.smalltalk }}
     steps: