diff --git a/lib/dao.js b/lib/dao.js
index 6595a576..3d76be09 100644
--- a/lib/dao.js
+++ b/lib/dao.js
@@ -1155,6 +1155,7 @@ DataAccessObject.prototype.updateAttributes = function updateAttributes(data, cb
             inst[key] = data[key];
             typedData[key] = inst[key];
             if (typeof typedData[key] === 'object' 
+              && typedData[key] !== null
               && typeof typedData[key].toObject === 'function') {
               typedData[key] = typedData[key].toObject();
             }