diff --git a/.eslintrc.js b/.eslintrc.js
index c4ae5e933a..304f8dba15 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -48,9 +48,7 @@ module.exports = {
       { ignorePureComponents: true },
     ],
     'react/jsx-no-bind': 'error',
-    // We still have too many files without the file annotation. Let's enable it
-    // once we flow-type everything.
-    // 'flowtype/require-valid-file-annotation': [ 'error', 'always', { annotationStyle: 'line' } ],
+    'flowtype/require-valid-file-annotation': [ 'error', 'always', { annotationStyle: 'line' } ],
     // no-dupe-keys crashes with recent eslint. See
     // https://github.com/gajus/eslint-plugin-flowtype/pull/266 and
     // https://github.com/gajus/eslint-plugin-flowtype/pull/302
diff --git a/bin/check-warn-yarn-changed.js b/bin/check-warn-yarn-changed.js
index 9b2bd17ce1..691ee93fe9 100644
--- a/bin/check-warn-yarn-changed.js
+++ b/bin/check-warn-yarn-changed.js
@@ -1,3 +1,4 @@
+// @noflow
 // MIT © Sindre Sorhus - sindresorhus.com
 // via https://gist.github.com/sindresorhus/7996717
 
diff --git a/bin/post-checkout.js b/bin/post-checkout.js
index 053532e264..bacc4b68b3 100644
--- a/bin/post-checkout.js
+++ b/bin/post-checkout.js
@@ -1,3 +1,4 @@
+// @noflow
 const [origHead, head, flag] = process.env.GIT_PARAMS.split(' ');
 
 // Flag is 1 if we moved between branches. Flag is 0 if we merely checked out a file from another branch.
diff --git a/bin/post-merge.js b/bin/post-merge.js
index afb291e645..5381a48193 100644
--- a/bin/post-merge.js
+++ b/bin/post-merge.js
@@ -1 +1,2 @@
+// @noflow
 require('./check-warn-yarn-changed.js')('ORIG_HEAD', 'HEAD');
diff --git a/bin/post-rewrite.js b/bin/post-rewrite.js
index feb428b654..a507e7a552 100644
--- a/bin/post-rewrite.js
+++ b/bin/post-rewrite.js
@@ -1,3 +1,4 @@
+// @noflow
 // This is either 'rebase' or 'amend'.
 if (process.env.GIT_PARAMS !== 'rebase') {
   process.exit();
diff --git a/server.js b/server.js
index 1ff5785b86..8431a42627 100644
--- a/server.js
+++ b/server.js
@@ -1,3 +1,4 @@
+// @noflow
 const webpack = require('webpack');
 const WebpackDevServer = require('webpack-dev-server');
 const config = require('./webpack.config');
diff --git a/webpack.config.js b/webpack.config.js
index 8582b081f3..c52888c50e 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -1,3 +1,4 @@
+// @noflow
 const path = require('path');
 const webpack = require('webpack');
 const HtmlWebpackPlugin = require('html-webpack-plugin');