diff --git a/zuul/main.yaml b/zuul/main.yaml
index d9f507fdcd..5c2b255035 100644
--- a/zuul/main.yaml
+++ b/zuul/main.yaml
@@ -1562,7 +1562,7 @@
 - tenant:
     name: zuul
     admin-rules: *admin_rules
-    default-ansible-version: 5
+    default-ansible-version: '5'
     max-nodes-per-job: 10
     source:
       gerrit: