diff --git a/lib/runtime/runtime.js b/lib/runtime/runtime.js
index 38178b4..12cce48 100644
--- a/lib/runtime/runtime.js
+++ b/lib/runtime/runtime.js
@@ -53,7 +53,7 @@ global._init = (function() {
     };
 
     global._start = function (data) {
-        Object.setPrototypeOf(data, null);
+        systemFunctions.Object.setPrototypeOf(data, null);
 
         let activeSegments, publicSegments, defaultPublicSegment, activeForeignSegment;
         let startTime, startDirtyTime = nowCpuTime();
diff --git a/lib/runtime/system-functions.js b/lib/runtime/system-functions.js
index 10ee31a..013a0aa 100644
--- a/lib/runtime/system-functions.js
+++ b/lib/runtime/system-functions.js
@@ -1,7 +1,8 @@
 const systemFunctions = {
     Object: {
         create: Object.create,
-        keys: Object.keys
+        keys: Object.keys,
+        setPrototypeOf: Object.setPrototypeOf
     },
     JSON: {
         stringify: JSON.stringify,