diff --git a/BE/src/study-logs/study-logs.service.ts b/BE/src/study-logs/study-logs.service.ts
index d995287..19f8f77 100644
--- a/BE/src/study-logs/study-logs.service.ts
+++ b/BE/src/study-logs/study-logs.service.ts
@@ -111,9 +111,10 @@ export class StudyLogsService {
     }));
 
     const result = {
-      total_time: (await this.calculateTotalTimes(user_id, date, date))[0],
+      total_time: (await this.calculateTotalTimes(user_id, date, date))[0] ?? 0,
       categories,
     };
+
     return result;
   }