diff --git a/wagtail/wagtailimages/migrations/0015_fill_filter_spec_field.py b/wagtail/wagtailimages/migrations/0015_fill_filter_spec_field.py
index 39755aeb3..651b4469e 100644
--- a/wagtail/wagtailimages/migrations/0015_fill_filter_spec_field.py
+++ b/wagtail/wagtailimages/migrations/0015_fill_filter_spec_field.py
@@ -4,32 +4,7 @@ from __future__ import unicode_literals
 
 from django.db import migrations
 
-
-def fill_filter_spec_forward(apps, schema_editor):
-    # Populate Rendition.filter_spec with the spec string of the corresponding Filter object
-    Rendition = apps.get_model('wagtailimages', 'Rendition')
-    db_alias = schema_editor.connection.alias
-    for rendition in Rendition.objects.using(db_alias).select_related('filter'):
-        rendition.filter_spec = rendition.filter.spec
-        rendition.save()
-
-
-def fill_filter_spec_reverse(apps, schema_editor):
-    # Populate the Rendition.filter
-    Rendition = apps.get_model('wagtailimages', 'Rendition')
-    Filter = apps.get_model('wagtailimages', 'Filter')
-    db_alias = schema_editor.connection.alias
-
-    filters_by_spec = {}
-    for rendition in Rendition.objects.using(db_alias):
-        try:
-            filter = filters_by_spec[rendition.filter_spec]
-        except KeyError:
-            filter, _ = Filter.objects.get_or_create(spec=rendition.filter_spec)
-            filters_by_spec[rendition.filter_spec] = filter
-
-        rendition.filter = filter
-        rendition.save()
+from wagtail.wagtailimages.utils import get_fill_filter_spec_migrations
 
 
 class Migration(migrations.Migration):
@@ -38,6 +13,7 @@ class Migration(migrations.Migration):
         ('wagtailimages', '0014_add_filter_spec_field'),
     ]
 
+    forward, reverse = get_fill_filter_spec_migrations('wagtailimages', 'Rendition')
     operations = [
-        migrations.RunPython(fill_filter_spec_forward, fill_filter_spec_reverse),
+        migrations.RunPython(forward, reverse),
     ]
diff --git a/wagtail/wagtailimages/utils.py b/wagtail/wagtailimages/utils.py
new file mode 100644
index 000000000..563571ad4
--- /dev/null
+++ b/wagtail/wagtailimages/utils.py
@@ -0,0 +1,34 @@
+from __future__ import absolute_import, unicode_literals
+
+
+# Helper functions for migrating the Rendition.filter foreign key to the filter_spec field,
+# and the corresponding reverse migration
+
+def get_fill_filter_spec_migrations(app_name, rendition_model_name):
+
+    def fill_filter_spec_forward(apps, schema_editor):
+        # Populate Rendition.filter_spec with the spec string of the corresponding Filter object
+        Rendition = apps.get_model(app_name, rendition_model_name)
+        db_alias = schema_editor.connection.alias
+        for rendition in Rendition.objects.using(db_alias).select_related('filter'):
+            rendition.filter_spec = rendition.filter.spec
+            rendition.save()
+
+    def fill_filter_spec_reverse(apps, schema_editor):
+        # Populate the Rendition.filter
+        Rendition = apps.get_model(app_name, rendition_model_name)
+        Filter = apps.get_model('wagtailimages', 'Filter')
+        db_alias = schema_editor.connection.alias
+
+        filters_by_spec = {}
+        for rendition in Rendition.objects.using(db_alias):
+            try:
+                filter = filters_by_spec[rendition.filter_spec]
+            except KeyError:
+                filter, _ = Filter.objects.get_or_create(spec=rendition.filter_spec)
+                filters_by_spec[rendition.filter_spec] = filter
+
+            rendition.filter = filter
+            rendition.save()
+
+    return (fill_filter_spec_forward, fill_filter_spec_reverse)