diff --git a/oyster/core.py b/oyster/core.py
index 194c99a..bb9ce69 100644
--- a/oyster/core.py
+++ b/oyster/core.py
@@ -83,7 +83,7 @@ class Kernel(object):
         self.doc_classes[doc_class] = properties
 
 
-    def track_url(self, url, doc_class, **kwargs):
+    def track_url(self, url, doc_class, id=None, **kwargs):
         """
         Add a URL to the set of tracked URLs, accessible via a given filename.
 
@@ -99,8 +99,11 @@ class Kernel(object):
         # if data is already tracked and this is just a duplicate call
         # return the original object
         if tracked:
+            # only check id if id was passed in
+            id_matches = (tracked['_id'] == id) if id else True
             if (tracked['metadata'] == kwargs and
-                tracked['doc_class'] == doc_class):
+                tracked['doc_class'] == doc_class and
+                id_matches):
                 return tracked['_id']
             else:
                 self.log('track', url=url, error='tracking conflict')
@@ -108,9 +111,13 @@ class Kernel(object):
                                  'metadata' % url)
 
         self.log('track', url=url)
-        return self.db.tracked.insert(dict(url=url, doc_class=doc_class,
-                                       _random=random.randint(0, sys.maxint),
-                                       versions=[], metadata=kwargs))
+
+        newdoc = dict(url=url, doc_class=doc_class,
+                      _random=random.randint(0, sys.maxint),
+                      versions=[], metadata=kwargs)
+        if id:
+            newdoc['_id'] = id
+        return self.db.tracked.insert(newdoc)
 
 
     def md5_versioning(self, olddata, newdata):
diff --git a/oyster/tests/test_kernel.py b/oyster/tests/test_kernel.py
index 7be0642..8d9c28b 100644
--- a/oyster/tests/test_kernel.py
+++ b/oyster/tests/test_kernel.py
@@ -78,12 +78,24 @@ class KernelTests(TestCase):
         id2 = self.kernel.track_url('http://example.com', 'default', pi=3)
         assert id1 == id2
 
-        # can't track same URL twice with different metadata
+        # test setting id
+        out = self.kernel.track_url('http://example.com/2', 'default',
+                                    'fixed-id')
+        assert out == 'fixed-id'
+
+        # can't track same URL twice with different id
+        assert_raises(ValueError, self.kernel.track_url, 'http://example.com',
+                      'default', 'hard-coded-id')
+        # logged error
+        assert self.kernel.db.logs.find_one({'error': 'tracking conflict'})
+
+        # ... with different metadata
         assert_raises(ValueError, self.kernel.track_url, 'http://example.com',
                       'default')
         # logged error
         assert self.kernel.db.logs.find_one({'error': 'tracking conflict'})
 
+        # ... different doc class
         assert_raises(ValueError, self.kernel.track_url, 'http://example.com',
                       'special-doc-class', pi=3)
         # logged error