diff --git a/swh/objstorage/exc.py b/swh/objstorage/exc.py
new file mode 100644
index 0000000..c90cdde
--- /dev/null
+++ b/swh/objstorage/exc.py
@@ -0,0 +1,25 @@
+# Copyright (C) 2015  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+
+class Error(Exception):
+
+    def __str__(self):
+        return 'storage error on object: %s' % self.args
+
+
+class ObjNotFoundError(Error):
+
+    def __str__(self):
+        return 'object not found: %s' % self.args
+
+
+class ObjStorageAPIError(Exception):
+    """ Specific internal exception of an object storage (mainly connection).
+    """
+
+    def __str__(self):
+        args = self.args
+        return 'An unexpected error occurred in the api backend: %s' % args