diff --git a/taiga/projects/issues/services.py b/taiga/projects/issues/services.py
index d646f30d..8f8b4a06 100644
--- a/taiga/projects/issues/services.py
+++ b/taiga/projects/issues/services.py
@@ -98,8 +98,8 @@ def issues_to_csv(project, queryset):
             "subject": issue.subject,
             "description": issue.description,
             "milestone": issue.milestone.name if issue.milestone else None,
-            "owner": issue.owner.username,
-            "owner_full_name": issue.owner.get_full_name(),
+            "owner": issue.owner.username if issue.owner else None,
+            "owner_full_name": issue.owner.get_full_name() if issue.owner else None,
             "assigned_to": issue.assigned_to.username if issue.assigned_to else None,
             "assigned_to_full_name": issue.assigned_to.get_full_name() if issue.assigned_to else None,
             "status": issue.status.name,
diff --git a/taiga/projects/tasks/services.py b/taiga/projects/tasks/services.py
index 46cbedfd..9e47eb5e 100644
--- a/taiga/projects/tasks/services.py
+++ b/taiga/projects/tasks/services.py
@@ -110,8 +110,8 @@ def tasks_to_csv(project, queryset):
             "description": task.description,
             "user_story": task.user_story.ref if task.user_story else None,
             "milestone": task.milestone.name if task.milestone else None,
-            "owner": task.owner.username,
-            "owner_full_name": task.owner.get_full_name(),
+            "owner": task.owner.username if task.owner else None,
+            "owner_full_name": task.owner.get_full_name() if task.owner else None,
             "assigned_to": task.assigned_to.username if task.assigned_to else None,
             "assigned_to_full_name": task.assigned_to.get_full_name() if task.assigned_to else None,
             "status": task.status.name,