diff --git a/.github/workflows/build_houdini.yml b/.github/workflows/build_houdini.yml
index e912423..55facec 100644
--- a/.github/workflows/build_houdini.yml
+++ b/.github/workflows/build_houdini.yml
@@ -18,7 +18,7 @@ jobs:
     environment: houdini
     strategy:
       matrix:
-        houdini_version: [19.5, 20.0]
+        houdini_version: ["19.5", "20.0"]
     steps:
       - name: Checkout repository
         uses: actions/checkout@v3
@@ -76,7 +76,7 @@ jobs:
     environment: houdini
     strategy:
       matrix:
-        houdini_version: [19.5, 20.0]
+        houdini_version: ["19.5", "20.0"]
     steps:
       - name: Checkout repository
         uses: actions/checkout@v3