diff --git a/lib/util/Util.js b/lib/util/Util.js
index b270d24..285b71f 100644
--- a/lib/util/Util.js
+++ b/lib/util/Util.js
@@ -122,10 +122,10 @@ class Util {
 
         let primaryKey = item.primaryKey;
         delete item.primaryKey;
-        if (!primaryKey.startsWith('<')) {
+        if (!primaryKey.startsWith('<') && !primaryKey.startsWith('_:')) {
           primaryKey = '<' + primaryKey;
         }
-        if (!primaryKey.endsWith('>')) {
+        if (!primaryKey.endsWith('>') && !primaryKey.startsWith('_:')) {
           primaryKey += '>';
         }