diff --git a/lib/odataServer.js b/lib/odataServer.js
index 0f2c2b8..d3227a6 100644
--- a/lib/odataServer.js
+++ b/lib/odataServer.js
@@ -256,7 +256,7 @@ ODataServer.prototype.bufferToBase64 = function(collection, res) {
     for (var i in res) {
         var doc = res[i];
         for (var prop in doc) {
-            if (!prop)
+            if (!prop || !entityType)
                 continue;
 
             var propDef = entityType[prop];