--- partition.py	2018-10-18 09:04:40.300721829 -0700
+++ partition2.py	2018-10-18 09:08:27.952565248 -0700
@@ -179,6 +179,8 @@

     def get_partition_number(self):
         """Return the partition number in the table."""
+        # Circular imports.
+        from maasserver.models.partitiontable import GPT_REQUIRED_SIZE
         # Sort manually instead of with `order_by`, this will prevent django
         # from making a query if the partitions are already cached.
         partitions_in_table = self.partition_table.partitions.all()
@@ -196,7 +198,10 @@
             block_device = self.partition_table.block_device
             if (arch == "ppc64el" and block_device.id == boot_disk.id):
                 return idx + 2
-            elif arch == "amd64" and bios_boot_method != "uefi":
+            elif (arch == "amd64" and
+                    self.partition_table.block_device.id == boot_disk.id and
+                    bios_boot_method != "uefi" and
+                    boot_disk.size >= GPT_REQUIRED_SIZE):
                 return idx + 2
             else:
                 return idx + 1