diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ef24e96..dc50908 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -29,7 +29,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, windows-latest]
         crystal_version: [latest]
-        experimental: false
+        experimental: [false]
         include:
           - os: ubuntu-latest
             crystal_version: 1.4.0