diff --git a/dataset/persistence/table.py b/dataset/persistence/table.py
index 8f930f2..4d729bf 100644
--- a/dataset/persistence/table.py
+++ b/dataset/persistence/table.py
@@ -56,7 +56,7 @@ class Table(object):
         self.database.engine.execute(q)
 
     def _ensure_columns(self, row, types={}):
-        for column in set(row.keys()) - set(self.columns.keys()):
+        for column in set(row.keys()) - set(self.table.columns.keys()):
             if column in types:
                 _type = types[column]
             else:
diff --git a/test/test_persistence.py b/test/test_persistence.py
index 68c4914..e10884f 100644
--- a/test/test_persistence.py
+++ b/test/test_persistence.py
@@ -2,16 +2,30 @@ import unittest
 from datetime import datetime
 
 from dataset import connect
+from sample_data import TEST_DATA
 
 class DatabaseTestCase(unittest.TestCase):
 
     def setUp(self):
         self.db = connect('sqlite:///:memory:')
+        self.tbl = self.db['weather']
+        for row in TEST_DATA:
+            self.tbl.insert(row)
 
     def test_create_table(self):
         table = self.db['foo']
         assert table.table.exists()
         assert len(table.table.columns) == 1, table.table.columns
+        assert 'id' in table.table.c, table.table.c
+
+    def test_load_table(self):
+        tbl = self.db.load_table('weather')
+        assert tbl.table==self.tbl.table
+
+    def test_query(self):
+        r = self.db.query('SELECT COUNT(*) AS num FROM weather').next()
+        assert r['num']==len(TEST_DATA), r
+
 
 
 if __name__ == '__main__':