diff --git a/dataset/table.py b/dataset/table.py
index 62a33a2..5e2bb76 100644
--- a/dataset/table.py
+++ b/dataset/table.py
@@ -247,7 +247,8 @@ class Table(object):
             with self.db.lock:
                 self._threading_warn()
                 for column in columns:
-                    self.db.op.add_column(self.name, column, self.db.schema)
+                    if not self.has_column(column.name):
+                        self.db.op.add_column(self.name, column, self.db.schema)
                 self._reflect_table()
 
     def _sync_columns(self, row, ensure, types=None):
diff --git a/setup.py b/setup.py
index d13a683..55261e9 100644
--- a/setup.py
+++ b/setup.py
@@ -8,7 +8,7 @@ if sys.version_info[:2] <= (2, 6):
 
 setup(
     name='dataset',
-    version='1.0.1',
+    version='1.0.2',
     description="Toolkit for Python-based database access.",
     long_description="",
     classifiers=[
@@ -19,7 +19,8 @@ setup(
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3.3',
         'Programming Language :: Python :: 3.4',
-        'Programming Language :: Python :: 3.5'
+        'Programming Language :: Python :: 3.5',
+        'Programming Language :: Python :: 3.6'
     ],
     keywords='sql sqlalchemy etl loading utility',
     author='Friedrich Lindenberg, Gregor Aisch, Stefan Wehrmeyer',