diff --git a/scaladoc/src/dotty/tools/scaladoc/Scaladoc.scala b/scaladoc/src/dotty/tools/scaladoc/Scaladoc.scala
index da34e97efdf5..95772655a964 100644
--- a/scaladoc/src/dotty/tools/scaladoc/Scaladoc.scala
+++ b/scaladoc/src/dotty/tools/scaladoc/Scaladoc.scala
@@ -207,7 +207,7 @@ object Scaladoc:
         classpath.get,
         bootclasspath.get,
         destFile,
-        siteRoot.nonDefault,
+        Option(siteRoot.withDefault(siteRoot.default)),
         projectVersion.nonDefault,
         projectLogo.nonDefault,
         projectFooter.nonDefault,