Index: frontend/src/components/SubjectCatalog/FavoriteButton.tsx
===================================================================
--- frontend/src/components/SubjectCatalog/FavoriteButton.tsx	(revision ad9b02260a77e6ee14e92636da6985c46453e71b)
+++ frontend/src/components/SubjectCatalog/FavoriteButton.tsx	(revision 80774d9928836ca3553bdf3fd83b67771ea260a3)
@@ -16,4 +16,5 @@
     const { isAuthenticated } = useAuth(); 
     const isFavorite = favoriteIds.has(subjectId);
+    const isFilled = isAuthenticated && isFavorite;
 
     return (
@@ -24,5 +25,5 @@
             aria-label={isFavorite ? 'Unfavorite' : 'Favorite'}
         >
-            <HeartIcon filled={isFavorite} />
+            <HeartIcon filled={isFilled} />
         </button>
     );