diff --git a/lib/index-file.js b/lib/index-file.js
index 88c08b5..443ae93 100644
--- a/lib/index-file.js
+++ b/lib/index-file.js
@@ -4,6 +4,12 @@ const fs = require('fs');
 const path = require('path');
 const Plugin = require('broccoli-plugin');
 
+const VERSION_STRATEGIES = {
+  EVERY_BUILD: 'every-build',
+  PROJECT_REVISION: 'project-revision',
+  PROJECT_VERSION: 'project-version'
+};
+
 function baseModule(options) {
   return `
     export const PROJECT_VERSION = '${options.projectVersion}';
@@ -48,17 +54,18 @@ module.exports = class Config extends Plugin {
     options.buildTime = (new Date).getTime() + '|' + Math.random();
 
     let module = baseModule(options);
-    let versionStrategy = options.versionStrategy;
+    let validVersionStrategies = [VERSION_STRATEGIES.EVERY_BUILD, VERSION_STRATEGIES.PROJECT_REVISION, VERSION_STRATEGIES.PROJECT_VERSION];
+    let versionStrategy = validVersionStrategies.indexOf(options.versionStrategy) !== -1 ? options.versionStrategy : VERSION_STRATEGIES.EVERY_BUILD;
 
-    if (!('versionStrategy' in options) || options.versionStrategy === 'every-build') {
+    if (versionStrategy === VERSION_STRATEGIES.EVERY_BUILD) {
       module += EVERY_BUILD_STRATEGY;
     }
 
-    if (options.versionStrategy === 'project-revision') {
+    if (versionStrategy === VERSION_STRATEGIES.PROJECT_REVISION) {
       module += PROJECT_REVISION_STRATEGY;
     }
 
-    if (options.versionStrategy === 'project-version') {
+    if (versionStrategy === VERSION_STRATEGIES.PROJECT_VERSION) {
       module += PROJECT_VERSION_STRATEGY;
     }