diff --git a/src/Dto/ResponseUserDto.cs b/src/Dto/ResponseUserDto.cs
index 79285f6..59a9117 100644
--- a/src/Dto/ResponseUserDto.cs
+++ b/src/Dto/ResponseUserDto.cs
@@ -22,7 +22,7 @@ public class ResponseUserDto
     public bool IsCoach { get; set; }
     public LargeImageDto? Image { get; set; }
     public ActivityTinyDto[] Activities { get; set; }
-    public DataSourceTinyDto DataSource { get; set; }
+    public DataSourceTinyDto? DataSource { get; set; }
     public FriendshipDto?[] Followers { get; set; }
     public FriendshipDto?[] Followings { get; set; }
 }
\ No newline at end of file
diff --git a/src/Entities2Dto/UserMappeur.cs b/src/Entities2Dto/UserMappeur.cs
index edc6b8c..0e8e4fe 100644
--- a/src/Entities2Dto/UserMappeur.cs
+++ b/src/Entities2Dto/UserMappeur.cs
@@ -81,7 +81,7 @@ public static class UserMappeur
         {
             userDto.Activities = athleteEntity.Activities.ToTinyDtos().ToArray();
             userDto.Image = athleteEntity.Image?.ToDto();
-            userDto.DataSource = athleteEntity.DataSource.ToTinyDto();
+            userDto.DataSource = athleteEntity.DataSource?.ToTinyDto();
             userDto.Followers = athleteEntity.Followers.ToTinyDtos().ToArray();
             userDto.Followings = athleteEntity.Followings.ToTinyDtos().ToArray();
         };
diff --git a/src/HeartTrackAPI/Controllers/ActivityController.cs b/src/HeartTrackAPI/Controllers/ActivityController.cs
index f117dfb..39f633d 100644
--- a/src/HeartTrackAPI/Controllers/ActivityController.cs
+++ b/src/HeartTrackAPI/Controllers/ActivityController.cs
@@ -71,7 +71,7 @@ public class ActivityController : Controller
             _logger.LogError("Athlete with id {id} not found", activityDto.AthleteId);
             return NotFound($"Athlete with id {activityDto.AthleteId} not found");
         }
-        if (activityDto.DataSourceId != null && user.DataSource.Id != activityDto.DataSourceId)
+        if (activityDto.DataSourceId != null && user.DataSource?.Id != activityDto.DataSourceId)
         {
             _logger.LogError("DataSource with id {id} not found for this user", activityDto.DataSourceId);
             return NotFound($"DataSource with id {activityDto.DataSourceId} not found");