diff --git a/.htmltest.yml b/.htmltest.yml
index 586616f83ea..8eed17e6398 100644
--- a/.htmltest.yml
+++ b/.htmltest.yml
@@ -1,6 +1,6 @@
 DirectoryPath: "public"
 EnforceHTTPS: true
-CheckDoctype: yes
+CheckDoctype: true
 CheckExternal: false
 IgnoreAltMissing: true
 IgnoreAltEmpty: false