Controller.backend_type is required
diff --git a/planetstack/core/models/site.py b/planetstack/core/models/site.py
index 67b77f5..cc2ad03 100644
--- a/planetstack/core/models/site.py
+++ b/planetstack/core/models/site.py
@@ -269,8 +269,8 @@
     deleted_objects = ControllerDeletionManager()
 
     name = models.CharField(max_length=200, unique=True, help_text="Name of the Controller")
+    backend_type = models.CharField(max_length=200, help_text="Type of compute controller, e.g. EC2, OpenStack, or OpenStack version")
     version = models.CharField(max_length=200, help_text="Controller version")
-    backend_type = models.CharField(max_length=200, null=True, blank=True, help_text="Type of compute controller, e.g. EC2, OpenStack, or OpenStack version")
     auth_url = models.CharField(max_length=200, null=True, blank=True, help_text="Auth url for the compute controller")
     admin_user = models.CharField(max_length=200, null=True, blank=True, help_text="Username of an admin user at this controller")
     admin_password = models.CharField(max_length=200, null=True, blank=True, help_text="Password of theadmin user at this controller")