diff --git a/lib/relation-definition.js b/lib/relation-definition.js
index 3d795bcf..001075a9 100644
--- a/lib/relation-definition.js
+++ b/lib/relation-definition.js
@@ -1431,8 +1431,9 @@ RelationDefinition.embedsMany = function hasMany(modelFrom, modelTo, params) {
         if (item instanceof modelTo) {
           if (!item.isValid()) {
             hasErrors = true;
+            var id = item[idName] || '(blank)';
             var first = Object.keys(item.errors)[0];
-            var msg = 'contains invalid item: `' + item[idName] + '`';
+            var msg = 'contains invalid item: `' + id + '`';
             msg += ' (' + first + ' ' + item.errors[first] + ')';
             this.errors.add(relationName, msg, 'invalid');
           }