diff --git a/imagekit/models/fields/__init__.py b/imagekit/models/fields/__init__.py
index 9556991..3f1a2f6 100644
--- a/imagekit/models/fields/__init__.py
+++ b/imagekit/models/fields/__init__.py
@@ -12,13 +12,13 @@ class SpecHostField(SpecHost):
 
         # Generate a spec_id to register the spec with. The default spec id is
         # "<app>:<model>_<field>"
-        if not getattr(self, 'spec_id', None):
+        if not spec_id:
             spec_id = (u'%s:%s:%s' % (cls._meta.app_label,
                             cls._meta.object_name, name)).lower()
 
-            # Register the spec with the id. This allows specs to be overridden
-            # later, from outside of the model definition.
-            super(SpecHostField, self).set_spec_id(spec_id)
+        # Register the spec with the id. This allows specs to be overridden
+        # later, from outside of the model definition.
+        super(SpecHostField, self).set_spec_id(spec_id)
 
 
 class ImageSpecField(SpecHostField):