diff --git a/apps/terminal/models.py b/apps/terminal/models.py
index 91ac8e052..5829fa2e1 100644
--- a/apps/terminal/models.py
+++ b/apps/terminal/models.py
@@ -127,7 +127,7 @@ class Session(models.Model):
     is_finished = models.BooleanField(default=False)
     has_replay = models.BooleanField(default=False, verbose_name=_("Replay"))
     has_command = models.BooleanField(default=False, verbose_name=_("Command"))
-    terminal = models.ForeignKey(Terminal, null=True, on_delete=models.CASCADE)
+    terminal = models.ForeignKey(Terminal, null=True, on_delete=models.SET_NULL)
     date_last_active = models.DateTimeField(verbose_name=_("Date last active"), default=timezone.now)
     date_start = models.DateTimeField(verbose_name=_("Date start"), db_index=True)
     date_end = models.DateTimeField(verbose_name=_("Date end"), null=True)
@@ -148,7 +148,7 @@ class Task(models.Model):
     id = models.UUIDField(default=uuid.uuid4, primary_key=True)
     name = models.CharField(max_length=128, choices=NAME_CHOICES, verbose_name=_("Name"))
     args = models.CharField(max_length=1024, verbose_name=_("Args"))
-    terminal = models.ForeignKey(Terminal, null=True, on_delete=models.CASCADE)
+    terminal = models.ForeignKey(Terminal, null=True, on_delete=models.SET_NULL)
     is_finished = models.BooleanField(default=False)
     date_created = models.DateTimeField(auto_now_add=True)
     date_finished = models.DateTimeField(null=True)
diff --git a/apps/terminal/tasks.py b/apps/terminal/tasks.py
index 89f9cc5cc..e267b30b7 100644
--- a/apps/terminal/tasks.py
+++ b/apps/terminal/tasks.py
@@ -31,6 +31,6 @@ def delete_terminal_status_period():
 def clean_orphan_session():
     active_sessions = Session.objects.filter(is_finished=False)
     for session in active_sessions:
-        if not session.terminal.is_active:
+        if not session.terminal or not session.terminal.is_active:
             session.is_finished = True
             session.save()