diff --git a/layerindex/migrations/0009_layerbranch_collection.py b/layerindex/migrations/0009_layerbranch_collection.py
new file mode 100644
index 0000000..bf6276f
--- /dev/null
+++ b/layerindex/migrations/0009_layerbranch_collection.py
@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('layerindex', '0008_yp_compatible'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='layerbranch',
+            name='collection',
+            field=models.CharField(help_text='Name of the collection that the layer provides for the purpose of expressing dependencies (as specified in BBFILE_COLLECTIONS). Can only contain letters, numbers and dashes.', max_length=40, blank=True, null=True, verbose_name='Layer Collection'),
+        ),
+    ]
diff --git a/layerindex/models.py b/layerindex/models.py
index e99f0b8..b39518a 100644
--- a/layerindex/models.py
+++ b/layerindex/models.py
@@ -157,7 +157,7 @@ class YPCompatibleVersion(models.Model):
 class LayerBranch(models.Model):
     layer = models.ForeignKey(LayerItem)
     branch = models.ForeignKey(Branch)
-    collection = models.CharField('Layer Collection', max_length=40, null=True, help_text='Name of the layer that could be used in the list of dependencies - can only contain letters, numbers and dashes')
+    collection = models.CharField('Layer Collection', max_length=40, null=True, blank=True, help_text='Name of the collection that the layer provides for the purpose of expressing dependencies (as specified in BBFILE_COLLECTIONS). Can only contain letters, numbers and dashes.')
     version = models.CharField('Layer Version', max_length=10, null=True, blank=True, help_text='The layer version for this particular branch.')
     vcs_subdir = models.CharField('Repository subdirectory', max_length=40, blank=True, help_text='Subdirectory within the repository where the layer is located, if not in the root (usually only used if the repository contains more than one layer)')
     vcs_last_fetch = models.DateTimeField('Last successful fetch', blank=True, null=True)