diff --git a/packages/metro/src/Resolver/polyfills/require.js b/packages/metro/src/Resolver/polyfills/require.js
index c86897ca..88f4109b 100644
--- a/packages/metro/src/Resolver/polyfills/require.js
+++ b/packages/metro/src/Resolver/polyfills/require.js
@@ -160,6 +160,11 @@ function unpackModuleId(
 }
 require.unpackModuleId = unpackModuleId;
 
+function packModuleId(value: {segmentId: number, localId: number}): ModuleID {
+  return value.segmentId << (ID_MASK_SHIFT + value.localId);
+}
+require.packModuleId = packModuleId;
+
 function loadModuleImplementation(moduleId, module) {
   const nativeRequire = global.nativeRequire;
   if (!module && nativeRequire) {
diff --git a/packages/metro/src/integration_tests/__tests__/__snapshots__/basic_bundle-test.js.snap b/packages/metro/src/integration_tests/__tests__/__snapshots__/basic_bundle-test.js.snap
index 3371a6f0..36c76c9d 100644
--- a/packages/metro/src/integration_tests/__tests__/__snapshots__/basic_bundle-test.js.snap
+++ b/packages/metro/src/integration_tests/__tests__/__snapshots__/basic_bundle-test.js.snap
@@ -66,15 +66,21 @@ exports[`basic_bundle bundles package with polyfills 1`] = `
 
   _require.unpackModuleId = unpackModuleId;
 
+  function packModuleId(value) {
+    return value.segmentId << ID_MASK_SHIFT + value.localId;
+  }
+
+  _require.packModuleId = packModuleId;
+
   function loadModuleImplementation(moduleId, module) {
     var nativeRequire = global.nativeRequire;
 
     if (!module && nativeRequire) {
       var _unpackModuleId = unpackModuleId(moduleId),
-          segmentId = _unpackModuleId.segmentId,
-          localId = _unpackModuleId.localId;
+          _segmentId = _unpackModuleId.segmentId,
+          _localId = _unpackModuleId.localId;
 
-      nativeRequire(localId, segmentId);
+      nativeRequire(_localId, _segmentId);
       module = modules[moduleId];
     }
 
@@ -251,15 +257,21 @@ exports[`basic_bundle bundles package without polyfills 1`] = `
 
   _require.unpackModuleId = unpackModuleId;
 
+  function packModuleId(value) {
+    return value.segmentId << ID_MASK_SHIFT + value.localId;
+  }
+
+  _require.packModuleId = packModuleId;
+
   function loadModuleImplementation(moduleId, module) {
     var nativeRequire = global.nativeRequire;
 
     if (!module && nativeRequire) {
       var _unpackModuleId = unpackModuleId(moduleId),
-          segmentId = _unpackModuleId.segmentId,
-          localId = _unpackModuleId.localId;
+          _segmentId = _unpackModuleId.segmentId,
+          _localId = _unpackModuleId.localId;
 
-      nativeRequire(localId, segmentId);
+      nativeRequire(_localId, _segmentId);
       module = modules[moduleId];
     }