diff --git a/chainsyncer/backend.py b/chainsyncer/backend.py
index 5953ff2..a5da1f4 100644
--- a/chainsyncer/backend.py
+++ b/chainsyncer/backend.py
@@ -79,7 +79,7 @@ class SyncerBackend:
         """
         self.connect()
         pair = self.db_object.cursor()
-        filter_state = self.db_object_filter.filter()
+        filter_state = self.db_object_filter.cursor()
         self.disconnect()
         return (pair, filter_state,)
    
@@ -95,7 +95,7 @@ class SyncerBackend:
         """
         self.connect()
         pair = self.db_object.set(block_height, tx_height)
-        filter_state = self.db_object_filter.filter()
+        filter_state = self.db_object_filter.cursor()
         self.disconnect()
         return (pair, filter_state,)
 
diff --git a/chainsyncer/db/models/filter.py b/chainsyncer/db/models/filter.py
index 656ed62..33964b7 100644
--- a/chainsyncer/db/models/filter.py
+++ b/chainsyncer/db/models/filter.py
@@ -54,11 +54,11 @@ class BlockchainSyncFilter(SessionBase):
 
 
     def start(self):
-        return self.flags_start
+        return int.from_bytes(self.flags_start, 'big')
 
 
     def cursor(self):
-        return self.flags_current
+        return int.from_bytes(self.flags, 'big')
 
 
     def clear(self):
@@ -68,12 +68,19 @@ class BlockchainSyncFilter(SessionBase):
     def target(self):
         n = 0
         for i in range(self.count):
-            n |= 2 << i
+            n |= (1 << self.count) - 1
         return n
 
 
     def set(self, n):
-        if self.flags & n > 0:
+        if n > self.count:
+            raise IndexError('bit flag out of range')
+
+        b = 1 << (n % 8)
+        i = int((n - 1) / 8 + 1)
+        if self.flags[i] & b > 0:
             SessionBase.release_session(session)
             raise AttributeError('Filter bit already set')
-        r.flags |= n
+        flags = bytearray(self.flags)
+        flags[i] |= b
+        self.flags = flags
diff --git a/chainsyncer/db/models/sync.py b/chainsyncer/db/models/sync.py
index 4f2f156..aafdd74 100644
--- a/chainsyncer/db/models/sync.py
+++ b/chainsyncer/db/models/sync.py
@@ -126,6 +126,7 @@ class BlockchainSync(SessionBase):
         """
         self.block_cursor = block_height
         self.tx_cursor = tx_height
+        return (self.block_cursor, self.tx_cursor,)
 
 
     def cursor(self):
diff --git a/tests/test_database.py b/tests/test_database.py
index 22f919b..ac3baf2 100644
--- a/tests/test_database.py
+++ b/tests/test_database.py
@@ -1,5 +1,6 @@
 # standard imports
 import unittest
+import logging
 
 # external imports
 from chainlib.chain import ChainSpec
@@ -12,6 +13,9 @@ from chainsyncer.backend import SyncerBackend
 # testutil imports
 from tests.base import TestBase
 
+logg = logging.getLogger()
+
+
 class TestDatabase(TestBase):
 
 
@@ -49,7 +53,31 @@ class TestDatabase(TestBase):
         session = SessionBase.create_session()
         o = session.query(BlockchainSyncFilter).get(filter_id)
         self.assertEqual(len(o.flags), 2)
+
+        t = o.target()
+        self.assertEqual(t, (1 << 9) - 1)
+
+        for i in range(9):
+            o.set(i)
+
+        c = o.cursor()
+        self.assertEqual(c, t)
+
         session.close()
 
+
+    def test_backend_resume(self):
+        s = SyncerBackend.live(self.chain_spec, 42)
+        s.register_filter('foo')
+        s.register_filter('bar')
+        s.register_filter('baz')
+
+        s.set(42, 13)
+
+        s = SyncerBackend.first(self.chain_spec)
+        logg.debug('start {}'.format(s))
+        self.assertEqual(s.get(), ((42,13), 0))
+        
+
 if __name__ == '__main__':
     unittest.main()