diff --git a/pubs/commands/import_cmd.py b/pubs/commands/import_cmd.py
index b83249a..09b721f 100644
--- a/pubs/commands/import_cmd.py
+++ b/pubs/commands/import_cmd.py
@@ -20,7 +20,7 @@ def parser(subparsers, conf):
             help="don't copy document files, just create a link.")
     parser.add_argument('keys', nargs='*',
             help="one or several keys to import from the file")
-    parser.add_argument('-O', '--overwrite', default=False,
+    parser.add_argument('-O', '--overwrite', action='store_true', default=False,
             help="Overwrite keys already in the database")
     return parser
 
diff --git a/tests/test_usecase.py b/tests/test_usecase.py
index 41b652a..78c3579 100644
--- a/tests/test_usecase.py
+++ b/tests/test_usecase.py
@@ -687,6 +687,26 @@ class TestUsecase(DataCommandTestCase):
         outs = self.execute_cmds(cmds)
         self.assertEqual(1 + 1, len(outs[-1].split('\n')))
 
+    def test_import_does_not_overwrite(self):
+        cmds = ['pubs init',
+                'pubs import data/ Page99',
+                'pubs import data/',
+                'pubs list'
+               ]
+
+        with self.assertRaises(FakeSystemExit):
+            self.execute_cmds(cmds)
+
+    def test_import_overwrites(self):
+        cmds = ['pubs init',
+                'pubs import data/ Page99',
+                'pubs import --overwrite data/ Page99',
+                'pubs list'
+               ]
+
+        outs = self.execute_cmds(cmds)
+        self.assertEqual(1 + 1, len(outs[-1].split('\n')))
+
     def test_update(self):
         cmds = ['pubs init',
                 'pubs add data/pagerank.bib',