diff --git a/multigtfs/models/feed.py b/multigtfs/models/feed.py
index 0aa7d95..1f45bd6 100644
--- a/multigtfs/models/feed.py
+++ b/multigtfs/models/feed.py
@@ -58,6 +58,20 @@ class Meta:
         db_table = 'feed'
         app_label = 'multigtfs'
 
+    _gtfs_order = [
+        Agency, Stop, Route, Service, ServiceDate, ShapePoint, Trip,
+        StopTime, Frequency, Fare, FareRule, Transfer, FeedInfo,
+    ]
+
+    @classmethod
+    def register_model(cls, klass):
+        cls._gtfs_order.append(klass)
+        return klass
+
+    @classmethod
+    def unregister_model(cls, klass):
+        cls._gtfs_order.remove(klass)
+
     def __str__(self):
         if self.name:
             return "%d %s" % (self.id, self.name)
@@ -88,14 +102,10 @@ def import_gtfs(self, gtfs_obj):
             opener = opener_from_zipfile(zfile)
             filelist = zfile.namelist()
 
-        gtfs_order = (
-            Agency, Stop, Route, Service, ServiceDate, ShapePoint, Trip,
-            StopTime, Frequency, Fare, FareRule, Transfer, FeedInfo,
-        )
         post_save.disconnect(dispatch_uid='post_save_shapepoint')
         post_save.disconnect(dispatch_uid='post_save_stop')
         try:
-            for klass in gtfs_order:
+            for klass in self._gtfs_order:
                 for f in filelist:
                     if f.endswith(klass._filename):
                         start_time = time.time()
@@ -155,12 +165,7 @@ def export_gtfs(self, gtfs_file):
         total_start = time.time()
         z = open_writable_zipfile(gtfs_file)
 
-        gtfs_order = (
-            Agency, Service, ServiceDate, Fare, FareRule, FeedInfo, Frequency,
-            Route, ShapePoint, StopTime, Stop, Transfer, Trip,
-        )
-
-        for klass in gtfs_order:
+        for klass in sorted(self._gtfs_order, key=lambda k: k._filename):
             start_time = time.time()
             content = klass.export_txt(self)
             if content: