diff --git a/packages/metro-bundler/src/lib/GlobalTransformCache.js b/packages/metro-bundler/src/lib/GlobalTransformCache.js
index 31d27cef..c0a03e1c 100644
--- a/packages/metro-bundler/src/lib/GlobalTransformCache.js
+++ b/packages/metro-bundler/src/lib/GlobalTransformCache.js
@@ -99,10 +99,11 @@ class KeyResultStore {
 }
 
 /**
- * The transform options contain absolute paths. This can contain, for
- * example, the username if someone works their home directory (very likely).
- * We need to get rid of this user-and-machine-dependent data for the global
- * cache, otherwise nobody  would share the same cache keys.
+ * The transform options contain absolute paths. This can contain, for example,
+ * the username if someone works their home directory (very likely). We get rid
+ * of this local data for the global cache, otherwise nobody would share the
+ * same cache keys. The project roots should not be needed as part of the cache
+ * key as they should not affect the transformation of a single particular file.
  */
 function globalizeTransformOptions(
   options: TransformOptions,
@@ -115,9 +116,7 @@ function globalizeTransformOptions(
     ...options,
     transform: {
       ...transform,
-      projectRoots: transform.projectRoots.map(p => {
-        return path.relative(path.join(__dirname, '../../../../..'), p);
-      }),
+      projectRoots: [],
     },
   };
 }
diff --git a/packages/metro-bundler/src/lib/__tests__/GlobalTransformCache-test.js b/packages/metro-bundler/src/lib/__tests__/GlobalTransformCache-test.js
index 1900ed85..17fee4a4 100644
--- a/packages/metro-bundler/src/lib/__tests__/GlobalTransformCache-test.js
+++ b/packages/metro-bundler/src/lib/__tests__/GlobalTransformCache-test.js
@@ -40,7 +40,7 @@ describe('GlobalTransformCache', () => {
       dev: true,
       minify: false,
       platform: 'ios',
-      transform: {projectRoots: [__dirname]},
+      transform: {},
     };
     const result = await Promise.all([cache.fetch({
       filePath: 'foo.js',
diff --git a/packages/metro-bundler/src/lib/__tests__/__snapshots__/GlobalTransformCache-test.js.snap b/packages/metro-bundler/src/lib/__tests__/__snapshots__/GlobalTransformCache-test.js.snap
index c0fdf1ad..70472f3a 100644
--- a/packages/metro-bundler/src/lib/__tests__/__snapshots__/GlobalTransformCache-test.js.snap
+++ b/packages/metro-bundler/src/lib/__tests__/__snapshots__/GlobalTransformCache-test.js.snap
@@ -19,12 +19,12 @@ Object {
 exports[`GlobalTransformCache fetches results 1`] = `
 Array [
   Object {
-    "code": "/* code from http://globalcache.com/2ad175cb80ae79fd33b914bfb392fb6742982d2a-foo.js */",
+    "code": "/* code from http://globalcache.com/17ce731dadd36402f15abb768843cb5e8ecf9ca7-foo.js */",
     "dependencies": Array [],
     "dependencyOffsets": Array [],
   },
   Object {
-    "code": "/* code from http://globalcache.com/d6c0a1a4199d572ab68b36c07d0d68607eebb131-bar.js */",
+    "code": "/* code from http://globalcache.com/d78572916bd877b6ac0e819e99be9fc2954f0e00-bar.js */",
     "dependencies": Array [],
     "dependencyOffsets": Array [],
   },