diff --git a/backend/profile/views/oj.py b/backend/profile/views/oj.py
index 3625a1df..81486202 100644
--- a/backend/profile/views/oj.py
+++ b/backend/profile/views/oj.py
@@ -197,10 +197,14 @@ def get(self, request):
                 create_time__lt=end_datetime,
             )
             .order_by("create_time")
-            .values_list("create_time", flat=True)
+            .values_list("problem_id", "create_time")
         )
+        solved_problem_ids = set()
         count_by_date = {}
-        for create_time in submissions:
+        for problem_id, create_time in submissions:
+            if problem_id in solved_problem_ids:
+                continue
+            solved_problem_ids.add(problem_id)
             activity_date = get_activity_service_date(create_time, current_timezone)
             count_by_date[activity_date] = count_by_date.get(activity_date, 0) + 1