diff --git a/service/keycloak/service.pkl b/service/keycloak/service.pkl
index b8c4e3f829c0ddfc4706aa1c47c188a4409b8f8d..e4b5ceba87a7e4822d39616028726aa1778dfa8c 100644
--- a/service/keycloak/service.pkl
+++ b/service/keycloak/service.pkl
@@ -11,7 +11,7 @@ class OpenIDClient extends service.Requirement {
   clientId: String(isNotEmpty)
   name: String
   redirectUris: Listing<String> = new { "*" }
-  usernameAliases: Map<String, String> = new {}
+  usernameAliases: Mapping<String, String> = new {}
 }
 
 local database = new postgres.Database { name = "keycloak_next" }