diff --git a/CameraRoll.js b/CameraRoll.js
index a353369..7a07bfd 100644
--- a/CameraRoll.js
+++ b/CameraRoll.js
@@ -8,41 +8,36 @@
  *
  * @providesModule CameraRoll
  * @flow
+ * @format
  */
 'use strict';
 
-var {PropTypes, checkPropTypes} = require('React');
-var RCTCameraRollManager = require('NativeModules').CameraRollManager;
+const {PropTypes, checkPropTypes} = require('React');
+const RCTCameraRollManager = require('NativeModules').CameraRollManager;
 
-var createStrictShapeTypeChecker = require('createStrictShapeTypeChecker');
-var deepFreezeAndThrowOnMutationInDev =
-  require('deepFreezeAndThrowOnMutationInDev');
-var invariant = require('fbjs/lib/invariant');
+const createStrictShapeTypeChecker = require('createStrictShapeTypeChecker');
+const invariant = require('fbjs/lib/invariant');
 
-var GROUP_TYPES_OPTIONS = [
-  'Album',
-  'All',
-  'Event',
-  'Faces',
-  'Library',
-  'PhotoStream',
-  'SavedPhotos', // default
-];
+const GROUP_TYPES_OPTIONS = {
+  Album: 'Album',
+  All: 'All',
+  Event: 'Event',
+  Faces: 'Faces',
+  Library: 'Library',
+  PhotoStream: 'PhotoStream',
+  SavedPhotos: 'SavedPhotos', // default
+};
 
-var ASSET_TYPE_OPTIONS = [
-  'All',
-  'Videos',
-  'Photos', // default
-];
-
-// Flow treats Object and Array as disjoint types, currently.
-deepFreezeAndThrowOnMutationInDev((GROUP_TYPES_OPTIONS: any));
-deepFreezeAndThrowOnMutationInDev((ASSET_TYPE_OPTIONS: any));
+const ASSET_TYPE_OPTIONS = {
+  All: 'All',
+  Videos: 'Videos',
+  Photos: 'Photos',
+};
 
 /**
  * Shape of the param arg for the `getPhotos` function.
  */
-var getPhotosParamChecker = createStrictShapeTypeChecker({
+const getPhotosParamChecker = createStrictShapeTypeChecker({
   /**
    * The number of photos wanted in reverse order of the photo application
    * (i.e. most recent first for SavedPhotos).
@@ -58,7 +53,7 @@ var getPhotosParamChecker = createStrictShapeTypeChecker({
   /**
    * Specifies which group types to filter the results to.
    */
-  groupTypes: PropTypes.oneOf(GROUP_TYPES_OPTIONS),
+  groupTypes: PropTypes.oneOf(Object.keys(GROUP_TYPES_OPTIONS)),
 
   /**
    * Specifies filter on group names, like 'Recent Photos' or custom album
@@ -69,7 +64,7 @@ var getPhotosParamChecker = createStrictShapeTypeChecker({
   /**
   * Specifies filter on asset type
   */
-  assetType: PropTypes.oneOf(ASSET_TYPE_OPTIONS),
+  assetType: PropTypes.oneOf(Object.keys(ASSET_TYPE_OPTIONS)),
 
   /**
    * Filter by mimetype (e.g. image/jpeg).
@@ -80,28 +75,30 @@ var getPhotosParamChecker = createStrictShapeTypeChecker({
 /**
  * Shape of the return value of the `getPhotos` function.
  */
-var getPhotosReturnChecker = createStrictShapeTypeChecker({
+const getPhotosReturnChecker = createStrictShapeTypeChecker({
   // $FlowFixMe(>=0.41.0)
-  edges: PropTypes.arrayOf(createStrictShapeTypeChecker({
-    node: createStrictShapeTypeChecker({
-      type: PropTypes.string.isRequired,
-      group_name: PropTypes.string.isRequired,
-      image: createStrictShapeTypeChecker({
-        uri: PropTypes.string.isRequired,
-        height: PropTypes.number.isRequired,
-        width: PropTypes.number.isRequired,
-        isStored: PropTypes.bool,
+  edges: PropTypes.arrayOf(
+    createStrictShapeTypeChecker({
+      node: createStrictShapeTypeChecker({
+        type: PropTypes.string.isRequired,
+        group_name: PropTypes.string.isRequired,
+        image: createStrictShapeTypeChecker({
+          uri: PropTypes.string.isRequired,
+          height: PropTypes.number.isRequired,
+          width: PropTypes.number.isRequired,
+          isStored: PropTypes.bool,
+        }).isRequired,
+        timestamp: PropTypes.number.isRequired,
+        location: createStrictShapeTypeChecker({
+          latitude: PropTypes.number,
+          longitude: PropTypes.number,
+          altitude: PropTypes.number,
+          heading: PropTypes.number,
+          speed: PropTypes.number,
+        }),
       }).isRequired,
-      timestamp: PropTypes.number.isRequired,
-      location: createStrictShapeTypeChecker({
-        latitude: PropTypes.number,
-        longitude: PropTypes.number,
-        altitude: PropTypes.number,
-        heading: PropTypes.number,
-        speed: PropTypes.number,
-      }),
-    }).isRequired,
-  })).isRequired,
+    }),
+  ).isRequired,
   page_info: createStrictShapeTypeChecker({
     has_next_page: PropTypes.bool.isRequired,
     start_cursor: PropTypes.string,
@@ -121,12 +118,13 @@ var getPhotosReturnChecker = createStrictShapeTypeChecker({
  *
  */
 class CameraRoll {
-
-  static GroupTypesOptions: Array<string>;
-  static AssetTypeOptions: Array<string>;
+  static GroupTypesOptions: Object = GROUP_TYPES_OPTIONS;
+  static AssetTypeOptions: Object = ASSET_TYPE_OPTIONS;
 
   static saveImageWithTag(tag: string): Promise<Object> {
-    console.warn('CameraRoll.saveImageWithTag is deprecated. Use CameraRoll.saveToCameraRoll instead');
+    console.warn(
+      'CameraRoll.saveImageWithTag is deprecated. Use CameraRoll.saveToCameraRoll instead',
+    );
     return this.saveToCameraRoll(tag, 'photo');
   }
 
@@ -144,16 +142,19 @@ class CameraRoll {
    *
    * Returns a Promise which will resolve with the new URI.
    */
-  static saveToCameraRoll(tag: string, type?: 'photo' | 'video'): Promise<Object> {
+  static saveToCameraRoll(
+    tag: string,
+    type?: 'photo' | 'video',
+  ): Promise<Object> {
     invariant(
       typeof tag === 'string',
-      'CameraRoll.saveToCameraRoll must be a valid string.'
+      'CameraRoll.saveToCameraRoll must be a valid string.',
     );
 
     invariant(
       type === 'photo' || type === 'video' || type === undefined,
       // $FlowFixMe(>=0.28.0)
-      `The second argument to saveToCameraRoll must be 'photo' or 'video'. You passed ${type}`
+      `The second argument to saveToCameraRoll must be 'photo' or 'video'. You passed ${type}`,
     );
 
     let mediaType = 'photo';
@@ -214,32 +215,39 @@ class CameraRoll {
    */
   static getPhotos(params) {
     if (__DEV__) {
-      checkPropTypes({params: getPhotosParamChecker}, {params}, 'params', 'CameraRoll.getPhotos');
+      checkPropTypes(
+        {params: getPhotosParamChecker},
+        {params},
+        'params',
+        'CameraRoll.getPhotos',
+      );
     }
     if (arguments.length > 1) {
-      console.warn('CameraRoll.getPhotos(tag, success, error) is deprecated.  Use the returned Promise instead');
+      console.warn(
+        'CameraRoll.getPhotos(tag, success, error) is deprecated.  Use the returned Promise instead',
+      );
       let successCallback = arguments[1];
       if (__DEV__) {
         const callback = arguments[1];
-        successCallback = (response) => {
+        successCallback = response => {
           checkPropTypes(
             {response: getPhotosReturnChecker},
             {response},
             'response',
-            'CameraRoll.getPhotos callback'
+            'CameraRoll.getPhotos callback',
           );
           callback(response);
         };
       }
-      const errorCallback = arguments[2] || ( () => {} );
-      RCTCameraRollManager.getPhotos(params).then(successCallback, errorCallback);
+      const errorCallback = arguments[2] || (() => {});
+      RCTCameraRollManager.getPhotos(params).then(
+        successCallback,
+        errorCallback,
+      );
     }
     // TODO: Add the __DEV__ check back in to verify the Promise result
     return RCTCameraRollManager.getPhotos(params);
   }
 }
 
-CameraRoll.GroupTypesOptions = GROUP_TYPES_OPTIONS;
-CameraRoll.AssetTypeOptions = ASSET_TYPE_OPTIONS;
-
 module.exports = CameraRoll;