diff --git a/model/sync-digest.h b/model/sync-digest.h
index 04e6d13..528180d 100644
--- a/model/sync-digest.h
+++ b/model/sync-digest.h
@@ -130,7 +130,9 @@
   uint32_t m_hashLength;
 };
 
+namespace Error {
 struct DigestCalculationError : virtual boost::exception, virtual std::exception { };
+}
 
 typedef boost::shared_ptr<Digest> DigestPtr;
 typedef boost::shared_ptr<const Digest> DigestConstPtr;