diff --git a/npm-jsx-list-lowercase-tags/index.js b/npm-jsx-list-lowercase-tags/index.js
new file mode 100755
index 0000000000000..e512add3a8a7a
--- /dev/null
+++ b/npm-jsx-list-lowercase-tags/index.js
@@ -0,0 +1,177 @@
+#!/usr/bin/env node
+
+var fs = require('fs');
+
+var types = require('ast-types');
+var esprima = require('esprima-fb');
+
+var namedTypes = types.namedTypes;
+
+var knownTags = {
+  a: true,
+  abbr: true,
+  address: true,
+  applet: true,
+  area: true,
+  article: true,
+  aside: true,
+  audio: true,
+  b: true,
+  base: true,
+  bdi: true,
+  bdo: true,
+  big: true,
+  blockquote: true,
+  body: true,
+  br: true,
+  button: true,
+  canvas: true,
+  caption: true,
+  circle: true,
+  cite: true,
+  code: true,
+  col: true,
+  colgroup: true,
+  command: true,
+  data: true,
+  datalist: true,
+  dd: true,
+  defs: true,
+  del: true,
+  details: true,
+  dfn: true,
+  dialog: true,
+  div: true,
+  dl: true,
+  dt: true,
+  ellipse: true,
+  em: true,
+  embed: true,
+  fieldset: true,
+  figcaption: true,
+  figure: true,
+  footer: true,
+  form: true,
+  g: true,
+  h1: true,
+  h2: true,
+  h3: true,
+  h4: true,
+  h5: true,
+  h6: true,
+  head: true,
+  header: true,
+  hgroup: true,
+  hr: true,
+  html: true,
+  i: true,
+  iframe: true,
+  img: true,
+  input: true,
+  ins: true,
+  kbd: true,
+  keygen: true,
+  label: true,
+  legend: true,
+  li: true,
+  line: true,
+  linearGradient: true,
+  link: true,
+  main: true,
+  map: true,
+  mark: true,
+  marquee: true,
+  mask: false,
+  menu: true,
+  menuitem: true,
+  meta: true,
+  meter: true,
+  nav: true,
+  noscript: true,
+  object: true,
+  ol: true,
+  optgroup: true,
+  option: true,
+  output: true,
+  p: true,
+  param: true,
+  path: true,
+  pattern: false,
+  polygon: true,
+  polyline: true,
+  pre: true,
+  progress: true,
+  q: true,
+  radialGradient: true,
+  rect: true,
+  rp: true,
+  rt: true,
+  ruby: true,
+  s: true,
+  samp: true,
+  script: true,
+  section: true,
+  select: true,
+  small: true,
+  source: true,
+  span: true,
+  stop: true,
+  strong: true,
+  style: true,
+  sub: true,
+  summary: true,
+  sup: true,
+  svg: true,
+  table: true,
+  tbody: true,
+  td: true,
+  text: true,
+  textarea: true,
+  tfoot: true,
+  th: true,
+  thead: true,
+  time: true,
+  title: true,
+  tr: true,
+  track: true,
+  tspan: true,
+  u: true,
+  ul: true,
+  'var': true,
+  video: true,
+  wbr: true
+};
+
+process.argv.slice(2).forEach(function(filename) {
+  fs.readFile(filename, 'utf8', function(err, code) {
+    if (err) {
+      console.log(err.message);
+      process.exit(1);
+    }
+
+    if (code.indexOf('@jsx') === -1) {
+      return;
+    }
+
+    try {
+      var ast = esprima.parse(code, {loc: true});
+    } catch (e) {
+      process.stderr.write(
+        '\x1B[31mError parsing ' + filename + ': ' + e + '\x1B[0m\n'
+      );
+      return;
+    }
+
+    types.traverse(ast, function(node) {
+      if (namedTypes.XJSOpeningElement.check(node) &&
+          /^[a-z]/.test(node.name.name) &&
+          !knownTags.hasOwnProperty(node.name.name)) {
+        console.log(
+          filename + ':' +
+          node.loc.start.line + ':' +
+          code.split('\n')[node.loc.start.line - 1]
+        );
+      }
+    });
+  });
+});
diff --git a/npm-jsx-list-lowercase-tags/package.json b/npm-jsx-list-lowercase-tags/package.json
new file mode 100644
index 0000000000000..28b0571bc94bd
--- /dev/null
+++ b/npm-jsx-list-lowercase-tags/package.json
@@ -0,0 +1,15 @@
+{
+  "name": "jsx-list-lowercase-tags",
+  "version": "0.1.0",
+  "description": "List lowercase user-defined JSX tags found in JavaScript files.",
+  "preferGlobal": true,
+  "bin": {
+    "jsx-list-lowercase-tags": "./index.js"
+  },
+  "author": "",
+  "license": "Apache-2.0",
+  "dependencies": {
+    "esprima-fb": "~3001.1.0-dev-harmony-fb",
+    "ast-types": "~0.3.28"
+  }
+}
diff --git a/vendor/fbtransform/transforms/react.js b/vendor/fbtransform/transforms/react.js
index 03d4880b826e8..38759b57f1c59 100644
--- a/vendor/fbtransform/transforms/react.js
+++ b/vendor/fbtransform/transforms/react.js
@@ -19,7 +19,6 @@
 var Syntax = require('esprima-fb').Syntax;
 var utils = require('jstransform/src/utils');
 
-var FALLBACK_TAGS = require('./xjs').knownTags;
 var renderXJSExpressionContainer =
   require('./xjs').renderXJSExpressionContainer;
 var renderXJSLiteral = require('./xjs').renderXJSLiteral;
@@ -62,7 +61,7 @@ function visitReactTag(traverse, object, path, state) {
        'Namespace tags are not supported. ReactJSX is not XML.');
   }
 
-  var isFallbackTag = FALLBACK_TAGS.hasOwnProperty(nameObject.name);
+  var isFallbackTag = /^[a-z]/.test(nameObject.name);
   utils.append(
     (isFallbackTag ? jsxObjIdent + '.' : '') + (nameObject.name) + '(',
     state
diff --git a/vendor/fbtransform/transforms/xjs.js b/vendor/fbtransform/transforms/xjs.js
index 66a8fb13cb247..b52cfa5364e6c 100644
--- a/vendor/fbtransform/transforms/xjs.js
+++ b/vendor/fbtransform/transforms/xjs.js
@@ -18,141 +18,6 @@
 var Syntax = require('esprima-fb').Syntax;
 var utils = require('jstransform/src/utils');
 
-var knownTags = {
-  a: true,
-  abbr: true,
-  address: true,
-  applet: true,
-  area: true,
-  article: true,
-  aside: true,
-  audio: true,
-  b: true,
-  base: true,
-  bdi: true,
-  bdo: true,
-  big: true,
-  blockquote: true,
-  body: true,
-  br: true,
-  button: true,
-  canvas: true,
-  caption: true,
-  circle: true,
-  cite: true,
-  code: true,
-  col: true,
-  colgroup: true,
-  command: true,
-  data: true,
-  datalist: true,
-  dd: true,
-  defs: true,
-  del: true,
-  details: true,
-  dfn: true,
-  dialog: true,
-  div: true,
-  dl: true,
-  dt: true,
-  ellipse: true,
-  em: true,
-  embed: true,
-  fieldset: true,
-  figcaption: true,
-  figure: true,
-  footer: true,
-  form: true,
-  g: true,
-  h1: true,
-  h2: true,
-  h3: true,
-  h4: true,
-  h5: true,
-  h6: true,
-  head: true,
-  header: true,
-  hgroup: true,
-  hr: true,
-  html: true,
-  i: true,
-  iframe: true,
-  img: true,
-  input: true,
-  ins: true,
-  kbd: true,
-  keygen: true,
-  label: true,
-  legend: true,
-  li: true,
-  line: true,
-  linearGradient: true,
-  link: true,
-  main: true,
-  map: true,
-  mark: true,
-  marquee: true,
-  mask: false,
-  menu: true,
-  menuitem: true,
-  meta: true,
-  meter: true,
-  nav: true,
-  noscript: true,
-  object: true,
-  ol: true,
-  optgroup: true,
-  option: true,
-  output: true,
-  p: true,
-  param: true,
-  path: true,
-  pattern: false,
-  polygon: true,
-  polyline: true,
-  pre: true,
-  progress: true,
-  q: true,
-  radialGradient: true,
-  rect: true,
-  rp: true,
-  rt: true,
-  ruby: true,
-  s: true,
-  samp: true,
-  script: true,
-  section: true,
-  select: true,
-  small: true,
-  source: true,
-  span: true,
-  stop: true,
-  strong: true,
-  style: true,
-  sub: true,
-  summary: true,
-  sup: true,
-  svg: true,
-  table: true,
-  tbody: true,
-  td: true,
-  text: true,
-  textarea: true,
-  tfoot: true,
-  th: true,
-  thead: true,
-  time: true,
-  title: true,
-  tr: true,
-  track: true,
-  tspan: true,
-  u: true,
-  ul: true,
-  'var': true,
-  video: true,
-  wbr: true
-};
-
 function renderXJSLiteral(object, isLast, state, start, end) {
   var lines = object.value.split(/\r\n|\n|\r/);
 
@@ -246,7 +111,6 @@ function trimLeft(value) {
   return value.replace(/^[ ]+/, '');
 }
 
-exports.knownTags = knownTags;
 exports.renderXJSExpressionContainer = renderXJSExpressionContainer;
 exports.renderXJSLiteral = renderXJSLiteral;
 exports.quoteAttrName = quoteAttrName;