diff --git a/components/style/gecko/wrapper.rs b/components/style/gecko/wrapper.rs
index 0c5e283cee7..20e9f9f3860 100644
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@@ -959,7 +959,8 @@ impl<'le> TElement for GeckoElement<'le> {
         // ::before/::after, XBL bindings, or nsIAnonymousContentCreators.
         if self.is_in_anonymous_subtree() ||
            self.has_xbl_binding_with_content() ||
-           self.is_in_shadow_tree() ||
+           self.is_html_slot_element() ||
+           self.shadow_root().is_some() ||
            self.may_have_anonymous_children() {
             unsafe {
                 let mut iter: structs::StyleChildrenIterator = ::std::mem::zeroed();