diff --git a/.travis.yml b/.travis.yml
index 2638532..3bb2c49 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -19,6 +19,5 @@ script:
 
 matrix:
     allow_failures:
-        # radicale db storage is broken in 0.8
+        # radicale db storage is broken in 0.8, all tests fail
         - env: DAV_SERVER=radicale RADICALE_BACKEND=database REQUIREMENTS=release
-        - env: DAV_SERVER=owncloud REQUIREMENTS=release
diff --git a/tests/storage/__init__.py b/tests/storage/__init__.py
index 9471738..a774529 100644
--- a/tests/storage/__init__.py
+++ b/tests/storage/__init__.py
@@ -162,3 +162,4 @@ class StorageTests(object):
         assert not s.has('asd')
         href, etag = s.upload(self._create_bogus_item(1))
         assert s.has(href)
+        assert not s.has('asd')
diff --git a/tests/storage/dav/test_main.py b/tests/storage/dav/test_main.py
index 2098841..b0257fa 100644
--- a/tests/storage/dav/test_main.py
+++ b/tests/storage/dav/test_main.py
@@ -91,6 +91,17 @@ class DavStorageTests(ServerMixin, StorageTests):
             pass
         assert not list(s.list())
 
+    @pytest.mark.xfail(dav_server == 'owncloud',
+                       reason='See issue #16')
+    def test_wrong_etag(self):
+        super(DavStorageTests, self).test_wrong_etag()
+
+    @pytest.mark.xfail(dav_server == 'owncloud',
+                       reason='See issue #16')
+    def test_update_nonexisting(self):
+        super(DavStorageTests, self).test_update_nonexisting()
+
+
 
 class TestCaldavStorage(DavStorageTests):
     storage_class = CaldavStorage
diff --git a/vdirsyncer/storage/base.py b/vdirsyncer/storage/base.py
index c342898..83f89c7 100644
--- a/vdirsyncer/storage/base.py
+++ b/vdirsyncer/storage/base.py
@@ -7,6 +7,7 @@
     :license: MIT, see LICENSE for more details.
 '''
 
+from .. import exceptions
 
 class Item(object):
 
@@ -80,6 +81,8 @@ class Storage(object):
         '''
         :param href: href to fetch
         :returns: (item, etag)
+        :raises: :exc:`vdirsyncer.exceptions.PreconditionFailed` if item can't
+            be found.
         '''
         raise NotImplementedError()
 
@@ -87,7 +90,7 @@ class Storage(object):
         '''
         :param hrefs: list of hrefs to fetch
         :raises: :exc:`vdirsyncer.exceptions.PreconditionFailed` if one of the
-        items couldn't be found.
+            items couldn't be found.
         :returns: iterable of (href, item, etag)
         '''
         for href in hrefs:
@@ -99,7 +102,12 @@ class Storage(object):
         check if item exists by href
         :returns: True or False
         '''
-        raise NotImplementedError()
+        try:
+            self.get(href)
+        except exceptions.PreconditionFailed:
+            return False
+        else:
+            return True
 
     def upload(self, item):
         '''
diff --git a/vdirsyncer/storage/dav.py b/vdirsyncer/storage/dav.py
index f9fcea0..181de99 100644
--- a/vdirsyncer/storage/dav.py
+++ b/vdirsyncer/storage/dav.py
@@ -189,14 +189,6 @@ class DavStorage(Storage):
             raise exceptions.NotFoundError(href)
         return rv
 
-    def has(self, href):
-        try:
-            self.get(href)
-        except exceptions.NotFoundError:
-            return False
-        else:
-            return True
-
     def _put(self, href, item, etag):
         headers = self._default_headers()
         headers['Content-Type'] = self.item_mimetype
diff --git a/vdirsyncer/storage/filesystem.py b/vdirsyncer/storage/filesystem.py
index 95eea69..b98efce 100644
--- a/vdirsyncer/storage/filesystem.py
+++ b/vdirsyncer/storage/filesystem.py
@@ -109,12 +109,16 @@ class FilesystemStorage(Storage):
 
     def get(self, href):
         fpath = self._get_filepath(href)
-        with open(fpath, 'rb') as f:
-            return (Item(f.read().decode(self.encoding)),
-                    _get_etag(fpath))
-
-    def has(self, href):
-        return os.path.isfile(self._get_filepath(href))
+        try:
+            with open(fpath, 'rb') as f:
+                return (Item(f.read().decode(self.encoding)),
+                        _get_etag(fpath))
+        except IOError as e:
+            import errno
+            if e.errno == errno.ENOENT:
+                raise exceptions.NotFoundError(href)
+            else:
+                raise
 
     def upload(self, item):
         href = self._get_href(item.uid)
diff --git a/vdirsyncer/storage/http.py b/vdirsyncer/storage/http.py
index 517fcb3..847e6f3 100644
--- a/vdirsyncer/storage/http.py
+++ b/vdirsyncer/storage/http.py
@@ -115,6 +115,3 @@ class HttpStorage(Storage):
     def get(self, href):
         x = self._items[href]
         return x, hashlib.sha256(x.raw).hexdigest()
-
-    def has(self, href):
-        return href in self._items