diff --git a/components/style/gecko/wrapper.rs b/components/style/gecko/wrapper.rs
index 5475be1e3fc..0ce4a45d175 100644
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@@ -178,11 +178,13 @@ impl<'lr> TShadowRoot for GeckoShadowRoot<'lr> {
                 as *const bindings::RawServoAuthorStyles)
         };
 
+
         let author_styles = AuthorStyles::<GeckoStyleSheet>::from_ffi(author_styles);
 
         debug_assert!(
             author_styles.quirks_mode == self.as_node().owner_doc().quirks_mode() ||
-                author_styles.stylesheets.is_empty()
+                author_styles.stylesheets.is_empty() ||
+                author_styles.stylesheets.dirty()
         );
 
         &author_styles.data