diff --git a/components/style/sharing/mod.rs b/components/style/sharing/mod.rs
index 8e56ed5f1a1..83ad650c5e2 100644
--- a/components/style/sharing/mod.rs
+++ b/components/style/sharing/mod.rs
@@ -751,6 +751,7 @@ impl<E: TElement> StyleSharingCache<E> {
         target: E,
     ) -> Option<PrimaryStyle> {
         self.cache_mut().lookup(|candidate| {
+            debug_assert_ne!(candidate.element, target);
             if !candidate.parent_style_identity().eq(inherited) {
                 return None;
             }