diff --git a/react-packager/src/node-haste/Cache/__tests__/Cache-test.js b/react-packager/src/node-haste/Cache/__tests__/Cache-test.js
index c466e50f..44b6c7b2 100644
--- a/react-packager/src/node-haste/Cache/__tests__/Cache-test.js
+++ b/react-packager/src/node-haste/Cache/__tests__/Cache-test.js
@@ -15,7 +15,7 @@ jest
 jest
   .mock('fs')
   .setMock('os', {
-    tmpDir() { return 'tmpDir'; },
+    tmpdir() { return 'tmpdir'; },
   });
 
 jest.useRealTimers();
diff --git a/react-packager/src/node-haste/Cache/index.js b/react-packager/src/node-haste/Cache/index.js
index 4e7f1237..12782f61 100644
--- a/react-packager/src/node-haste/Cache/index.js
+++ b/react-packager/src/node-haste/Cache/index.js
@@ -16,8 +16,7 @@ const denodeify = require('denodeify');
 const fs = require('graceful-fs');
 const isAbsolutePath = require('absolute-path');
 const path = require('path');
-/* $FlowFixMe: missing function definition. */
-const tmpDir = require('os').tmpDir();
+const tmpDir = require('os').tmpdir();
 
 function getObjectValues<T>(object: {[key: string]: T}): Array<T> {
   return Object.keys(object).map(key => object[key]);