diff --git a/judge/ml/collab_filter.py b/judge/ml/collab_filter.py
index 76f8827..504f9c6 100644
--- a/judge/ml/collab_filter.py
+++ b/judge/ml/collab_filter.py
@@ -45,7 +45,7 @@ class CollabFilter:
             if pid < len(scores):
                 res.append((scores[pid], problem))
 
-        res.sort(reverse=True)
+        res.sort(reverse=True, key=lambda x: x[0])
         return res[:limit]
 
 
@@ -60,5 +60,5 @@ class CollabFilter:
         for p in problemset:
             if p.id < len(scores):
                 res.append((scores[p.id], p))
-        res.sort(reverse=True)
+        res.sort(reverse=True, key=lambda x: x[0])
         return res[:limit]
\ No newline at end of file
diff --git a/judge/views/problem.py b/judge/views/problem.py
index 25bf526..f58fd11 100644
--- a/judge/views/problem.py
+++ b/judge/views/problem.py
@@ -646,8 +646,9 @@ class ProblemFeed(FeedView):
         cl_model = CollabFilter()
         dot_rec = cl_model.user_recommendations(user, queryset, cl_model.DOT, 100)
         cosine_rec = cl_model.user_recommendations(user, queryset, cl_model.COSINE, 100)
-        hot_problems_rec = hot_problems(timedelta(days=7), 10)
-        
+        hot_problems_rec = [problem for problem in hot_problems(timedelta(days=7), 10)
+                                    if problem in queryset]
+
         q = self.merge_recommendation([dot_rec, cosine_rec, hot_problems_rec])
         return q