diff --git a/netbox/circuits/migrations/0008_circuittermination_interface_protect_on_delete.py b/netbox/circuits/migrations/0008_circuittermination_interface_protect_on_delete.py
new file mode 100644
index 000000000..14ee6686d
--- /dev/null
+++ b/netbox/circuits/migrations/0008_circuittermination_interface_protect_on_delete.py
@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11 on 2017-04-19 17:17
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('circuits', '0007_circuit_add_description'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='circuittermination',
+            name='interface',
+            field=models.OneToOneField(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='circuit_termination', to='dcim.Interface'),
+        ),
+    ]
diff --git a/netbox/circuits/models.py b/netbox/circuits/models.py
index 6a0380dd5..caa91d1a3 100644
--- a/netbox/circuits/models.py
+++ b/netbox/circuits/models.py
@@ -150,10 +150,14 @@ class CircuitTermination(models.Model):
     circuit = models.ForeignKey('Circuit', related_name='terminations', on_delete=models.CASCADE)
     term_side = models.CharField(max_length=1, choices=TERM_SIDE_CHOICES, verbose_name='Termination')
     site = models.ForeignKey('dcim.Site', related_name='circuit_terminations', on_delete=models.PROTECT)
-    interface = models.OneToOneField('dcim.Interface', related_name='circuit_termination', blank=True, null=True)
+    interface = models.OneToOneField(
+        'dcim.Interface', related_name='circuit_termination', blank=True, null=True, on_delete=models.PROTECT
+    )
     port_speed = models.PositiveIntegerField(verbose_name='Port speed (Kbps)')
-    upstream_speed = models.PositiveIntegerField(blank=True, null=True, verbose_name='Upstream speed (Kbps)',
-                                                 help_text='Upstream speed, if different from port speed')
+    upstream_speed = models.PositiveIntegerField(
+        blank=True, null=True, verbose_name='Upstream speed (Kbps)',
+        help_text='Upstream speed, if different from port speed'
+    )
     xconnect_id = models.CharField(max_length=50, blank=True, verbose_name='Cross-connect ID')
     pp_info = models.CharField(max_length=100, blank=True, verbose_name='Patch panel/port(s)')