diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 689b29e..1d0f32e 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -13,6 +13,8 @@ jobs:
         include:
           - xcode: "16.0" # Swift 6
             macOS: "14"
+          - xcode: "15.4" # Swift 5.9
+            macOS: "14"
       fail-fast: false
 
     runs-on: macos-${{ matrix.macOS }}