diff --git a/README.md b/README.md
index a498379..ec5c858 100644
--- a/README.md
+++ b/README.md
@@ -115,6 +115,10 @@ Maps the specified path parameter `name` to a specialized param-capturing middle
 
 This function positions the middleware in the same stack as `.use`.
 
+If a `Promise` is returned from the `param_middleware` function, the router
+will attach an `onRejected` callback using `.then(null, onRejected)`. If the promise is rejected,
+`next` will be called with the rejected value as the error, or `new Error...` if the value is falsy.
+
 Parameter mapping is used to provide pre-conditions to routes
 which use normalized placeholders. For example a _:user_id_ parameter
 could automatically load a user's information from the database without
diff --git a/index.js b/index.js
index 45495b3..874d5b2 100644
--- a/index.js
+++ b/index.js
@@ -13,6 +13,7 @@
  */
 
 var flatten = require('array-flatten').flatten
+var isPromise = require('is-promise')
 var Layer = require('./lib/layer')
 var methods = require('methods')
 var mixin = require('utils-merge')
@@ -634,7 +635,12 @@ function processParams (params, layer, called, req, res, done) {
     if (!fn) return param()
 
     try {
-      fn(req, res, paramCallback, paramVal, key.name)
+      var ret = fn(req, res, paramCallback, paramVal, key.name)
+      if (isPromise(ret)) {
+        ret.then(null, function (error) {
+          paramCallback(error || new Error('Rejected promise'))
+        })
+      }
     } catch (e) {
       paramCallback(e)
     }
diff --git a/lib/layer.js b/lib/layer.js
index 39acfe2..4936ca2 100644
--- a/lib/layer.js
+++ b/lib/layer.js
@@ -12,6 +12,7 @@
  * @private
  */
 
+var isPromise = require('is-promise')
 var pathRegexp = require('path-to-regexp')
 
 /**
@@ -187,20 +188,6 @@ function decodeParam (val) {
   }
 }
 
-/**
- * Returns true if the val is a Promise.
- *
- * @param {*} val
- * @return {boolean}
- * @private
- */
-
-function isPromise (val) {
-  return val &&
-    typeof val === 'object' &&
-    typeof val.then === 'function'
-}
-
 /**
  * Loosens the given path for path-to-regexp matching.
  */
diff --git a/package.json b/package.json
index 9b6306c..58bc285 100644
--- a/package.json
+++ b/package.json
@@ -10,6 +10,7 @@
   "repository": "pillarjs/router",
   "dependencies": {
     "array-flatten": "3.0.0",
+    "is-promise": "4.0.0",
     "methods": "~1.1.2",
     "parseurl": "~1.3.3",
     "path-to-regexp": "3.2.0",
diff --git a/test/param.js b/test/param.js
index 43245fc..98bef58 100644
--- a/test/param.js
+++ b/test/param.js
@@ -1,4 +1,3 @@
-
 var after = require('after')
 var Router = require('..')
 var utils = require('./support/utils')
@@ -10,6 +9,8 @@ var shouldNotHitHandle = utils.shouldNotHitHandle
 var createServer = utils.createServer
 var request = utils.request
 
+var describePromises = global.Promise ? describe : describe.skip
+
 describe('Router', function () {
   describe('.param(name, fn)', function () {
     it('should reject missing name', function () {
@@ -253,6 +254,25 @@ describe('Router', function () {
         .get('/user/bob')
         .expect(500, /Error: boom/, done)
     })
+    describePromises('promise support', function () {
+      it('should catch rejected promises returned from fn', function (done) {
+        var router = new Router()
+        var server = createServer(router)
+
+        router.param('user', function parseUser (req, res, next, user) {
+          return Promise.reject(new Error('boom'))
+        })
+
+        router.get('/user/:user', function (req, res) {
+          res.setHeader('Content-Type', 'text/plain')
+          res.end('get user ' + req.params.id)
+        })
+
+        request(server)
+          .get('/user/bob')
+          .expect(500, /Error: boom/, done)
+      })
+    })
 
     describe('next("route")', function () {
       it('should cause route with param to be skipped', function (done) {
diff --git a/test/router.js b/test/router.js
index 74308f7..7163ee5 100644
--- a/test/router.js
+++ b/test/router.js
@@ -813,6 +813,24 @@ describe('Router', function () {
             .expect(200, 'saw Error: boom!', done)
         })
       })
+      it('should invoke error function after router.param returns rejected promise', function (done) {
+        var router = new Router()
+        var server = createServer(router)
+
+        router.param('user', function (req, res, next, user) {
+          return Promise.reject(new Error('boom!'))
+        })
+
+        router.get('/:user', function handle (req, res, next) {
+          res.end()
+        })
+
+        router.use(sawError)
+
+        request(server)
+          .get('/username')
+          .expect(200, 'saw Error: boom!', done)
+      })
     })
 
     describe('req.baseUrl', function () {