diff --git a/src/options.js b/src/options.js
index 1456be6360..3439e0ccd9 100755
--- a/src/options.js
+++ b/src/options.js
@@ -1,15 +1,8 @@
-/* @flow */
 // A second optional argument can be given to further configure
 // the parser process. These options are recognized:
 
-export const defaultOptions: {
-  sourceType: string,
-  allowReturnOutsideFunction: boolean,
-  allowImportExportEverywhere: boolean,
-  allowSuperOutsideMethod: boolean,
-  plugins: Array<string>,
-  strictMode: any
-} = {
+
+export const defaultOptions = {
   // Source type ("script" or "module") for different semantics
   sourceType: "script",
   // When enabled, a return at the top level is not considered an
@@ -28,7 +21,7 @@ export const defaultOptions: {
 
 // Interpret and default an options object
 
-export function getOptions(opts?: Object): Object {
+export function getOptions(opts) {
   let options = {};
   for (let key in defaultOptions) {
     options[key] = opts && key in opts ? opts[key] : defaultOptions[key];
diff --git a/src/parser/comments.js b/src/parser/comments.js
index 9fabbed737..f1a266b58a 100644
--- a/src/parser/comments.js
+++ b/src/parser/comments.js
@@ -1,4 +1,3 @@
-/* @flow */
 /* eslint max-len: 0 */
 
 /**
@@ -119,7 +118,7 @@ pp.processComment = function (node) {
       // result in an empty array, and if so, the array must be
       // deleted.
       node.leadingComments = this.state.leadingComments.slice(0, i);
-      if ((node.leadingComments: Array<any>).length === 0) {
+      if (node.leadingComments.length === 0) {
         node.leadingComments = null;
       }
 
diff --git a/src/parser/index.js b/src/parser/index.js
index bc034e0549..7be5ec3bae 100644
--- a/src/parser/index.js
+++ b/src/parser/index.js
@@ -1,4 +1,3 @@
-/* @flow */
 
 import { reservedWords } from "../util/identifier";
 import { getOptions } from "../options";
@@ -7,7 +6,7 @@ import Tokenizer from "../tokenizer";
 export const plugins = {};
 
 export default class Parser extends Tokenizer {
-  constructor(options: Object, input: string) {
+  constructor(options, input) {
     options = getOptions(options);
     super(options, input);
 
@@ -23,15 +22,15 @@ export default class Parser extends Tokenizer {
     }
   }
 
-  hasPlugin(name: string): boolean {
+  hasPlugin(name) {
     return !!(this.plugins["*"] || this.plugins[name]);
   }
 
-  extend(name: string, f: Function) {
+  extend(name, f) {
     this[name] = f(this[name]);
   }
 
-  loadPlugins(plugins: Array<string>): Object {
+  loadPlugins(plugins) {
     let pluginMap = {};
 
     if (plugins.indexOf("flow") >= 0) {
@@ -52,13 +51,7 @@ export default class Parser extends Tokenizer {
     return pluginMap;
   }
 
-  parse(): {
-    type: "File",
-    program: {
-      type: "Program",
-      body: Array<Object>
-    }
-  } {
+  parse() {
     let file = this.startNode();
     let program = this.startNode();
     this.nextToken();
diff --git a/src/parser/util.js b/src/parser/util.js
index 03ca0b2e57..240f6c672e 100644
--- a/src/parser/util.js
+++ b/src/parser/util.js
@@ -1,4 +1,3 @@
-/* @flow */
 
 import { types as tt } from "../tokenizer/types";
 import Parser from "./index";
diff --git a/src/tokenizer/context.js b/src/tokenizer/context.js
index bd35e67860..3e158b915e 100644
--- a/src/tokenizer/context.js
+++ b/src/tokenizer/context.js
@@ -1,4 +1,3 @@
-/* @flow */
 
 // The algorithm used to determine whether a regexp can appear at a
 // given point in the program is loosely based on sweet.js' approach.
@@ -8,27 +7,16 @@ import { types as tt } from "./types";
 import { lineBreak } from "../util/whitespace";
 
 export class TokContext {
-  constructor(
-    token: string,
-    isExpr?: boolean,
-    preserveSpace?: boolean,
-    override?: Function,
-  ) {
+  constructor(token, isExpr, preserveSpace, override) {
     this.token = token;
     this.isExpr = !!isExpr;
     this.preserveSpace = !!preserveSpace;
     this.override = override;
   }
 
-  token: string;
-  isExpr: boolean;
-  preserveSpace: boolean;
-  override: ?Function;
 }
 
-export const types: {
-  [key: string]: TokContext;
-} = {
+export const types = {
   b_stat: new TokContext("{", false),
   b_expr: new TokContext("{", true),
   b_tmpl: new TokContext("${", true),
diff --git a/src/tokenizer/index.js b/src/tokenizer/index.js
index e4a7b4ddc8..8dd238c8a7 100644
--- a/src/tokenizer/index.js
+++ b/src/tokenizer/index.js
@@ -1,8 +1,7 @@
-/* @noflow */
+import { isIdentifierStart, isIdentifierChar, isKeyword } from "../util/identifier";
 /* eslint max-len: 0 */
 /* eslint indent: 0 */
 
-import type { TokenType } from "./types";
 import { isIdentifierStart, isIdentifierChar, isKeyword } from "../util/identifier";
 import { types as tt, keywords as keywordTypes } from "./types";
 import { types as ct } from "./context";
@@ -23,11 +22,6 @@ export class Token {
     this.loc = new SourceLocation(state.startLoc, state.endLoc);
   }
 
-  type: TokenType;
-  value: any;
-  start: number;
-  end: number;
-  loc: SourceLocation;
 }
 
 // ## Tokenizer
diff --git a/src/util/whitespace.js b/src/util/whitespace.js
index 50b90c8ca7..4463c8e549 100644
--- a/src/util/whitespace.js
+++ b/src/util/whitespace.js
@@ -1,4 +1,3 @@
-/* @flow */
 
 // Matches a whole line break (where CRLF is considered a single
 // line break). Used to count lines.
@@ -6,7 +5,7 @@
 export const lineBreak = /\r\n?|\n|\u2028|\u2029/;
 export const lineBreakG = new RegExp(lineBreak.source, "g");
 
-export function isNewLine(code: number): boolean {
+export function isNewLine(code) {
   return code === 10 || code === 13 || code === 0x2028 || code === 0x2029;
 }