diff --git a/src/packagers/JSConcatPackager.js b/src/packagers/JSConcatPackager.js
index 89fe42d0889..52f69393947 100644
--- a/src/packagers/JSConcatPackager.js
+++ b/src/packagers/JSConcatPackager.js
@@ -1,27 +1,22 @@
 const Packager = require('./Packager');
 const path = require('path');
-const fs = require('fs');
 const concat = require('../scope-hoisting/concat');
 const urlJoin = require('../utils/urlJoin');
+const getExisting = require('../utils/getExisting');
 const walk = require('babylon-walk');
 const babylon = require('babylon');
 const t = require('babel-types');
 const {getName, getIdentifier} = require('../scope-hoisting/utils');
 
-const prelude = {
-  source: fs
-    .readFileSync(path.join(__dirname, '../builtins/prelude2.js'), 'utf8')
-    .trim(),
-  minified: fs
-    .readFileSync(path.join(__dirname, '../builtins/prelude2.min.js'), 'utf8')
-    .trim()
-    .replace(/;$/, '')
-};
-
-const helpers =
-  fs
-    .readFileSync(path.join(__dirname, '../builtins/helpers.js'), 'utf8')
-    .trim() + '\n';
+const prelude = getExisting(
+  path.join(__dirname, '../builtins/prelude2.min.js'),
+  path.join(__dirname, '../builtins/prelude2.js')
+);
+
+const helpers = getExisting(
+  path.join(__dirname, '../builtins/helpers.min.js'),
+  path.join(__dirname, '../builtins/helpers.js')
+);
 
 class JSConcatPackager extends Packager {
   async start() {
diff --git a/src/packagers/JSPackager.js b/src/packagers/JSPackager.js
index ed72b808f8a..ed2f8c17a74 100644
--- a/src/packagers/JSPackager.js
+++ b/src/packagers/JSPackager.js
@@ -1,19 +1,14 @@
-const fs = require('fs');
 const path = require('path');
 const Packager = require('./Packager');
+const getExisting = require('../utils/getExisting');
 const urlJoin = require('../utils/urlJoin');
 const lineCounter = require('../utils/lineCounter');
 const objectHash = require('../utils/objectHash');
 
-const prelude = {
-  source: fs
-    .readFileSync(path.join(__dirname, '../builtins/prelude.js'), 'utf8')
-    .trim(),
-  minified: fs
-    .readFileSync(path.join(__dirname, '../builtins/prelude.min.js'), 'utf8')
-    .trim()
-    .replace(/;$/, '')
-};
+const prelude = getExisting(
+  path.join(__dirname, '../builtins/prelude.min.js'),
+  path.join(__dirname, '../builtins/prelude.js')
+);
 
 class JSPackager extends Packager {
   async start() {
diff --git a/src/utils/getExisting.js b/src/utils/getExisting.js
new file mode 100644
index 00000000000..6d6dcfc8e32
--- /dev/null
+++ b/src/utils/getExisting.js
@@ -0,0 +1,16 @@
+const fs = require('fs');
+/**
+ * Creates an object that contains both source and minified
+ * source (using the source as a fallback).
+ * e.g. builtins.min.js and builtins.js.
+ */
+module.exports = function(minified, source) {
+  var sourceFile = fs.readFileSync(source, 'utf8').trim();
+  return {
+    source: sourceFile,
+    minified: fs.existsSync(minified) ? fs
+      .readFileSync(minified, 'utf8')
+      .trim()
+      .replace(/;$/, '') : sourceFile
+  }
+};