diff --git a/imagekit/models/fields/__init__.py b/imagekit/models/fields/__init__.py
index 771c81e..3f98f35 100644
--- a/imagekit/models/fields/__init__.py
+++ b/imagekit/models/fields/__init__.py
@@ -43,8 +43,8 @@ class ImageSpecField(SpecHostField):
         self.set_spec_id(cls, name)
 
         # Add the model and field as a source for this spec id
-        specs.registry.add_source(ImageFieldSpecSource(cls, self.image_field),
-                                 self.spec_id)
+        specs.registry.add_sources(self.spec_id,
+                [ImageFieldSpecSource(cls, self.image_field)])
 
 
 class ProcessedImageField(models.ImageField, SpecHostField):
diff --git a/imagekit/specs/__init__.py b/imagekit/specs/__init__.py
index 3d5e0ca..3e761a6 100644
--- a/imagekit/specs/__init__.py
+++ b/imagekit/specs/__init__.py
@@ -53,8 +53,8 @@ class SpecRegistry(object):
             raise AlreadyRegistered('The spec with id %s is already registered' % id)
         self._specs[id] = spec
 
-        for source in getattr(config, 'sources', None) or []:
-            self.add_source(source, id)
+        sources = getattr(config, 'sources', None) or []
+        self.add_sources(id, sources)
 
     def unregister(self, id, spec):
         try:
@@ -72,14 +72,15 @@ class SpecRegistry(object):
         else:
             return spec
 
-    def add_source(self, source, spec_id):
+    def add_sources(self, spec_id, sources):
         """
-        Associates a source with a spec id
+        Associates sources with a spec id
 
         """
-        if source not in self._sources:
-            self._sources[source] = set()
-        self._sources[source].add(spec_id)
+        for source in sources:
+            if source not in self._sources:
+                self._sources[source] = set()
+            self._sources[source].add(spec_id)
 
     def before_access_receiver(self, sender, spec, file, **kwargs):
         spec.image_cache_strategy.invoke_callback('before_access', file)