diff --git a/README.md b/README.md
index d834889..4302e1d 100644
--- a/README.md
+++ b/README.md
@@ -157,10 +157,14 @@ var server = new Server({
     // This example only allows one torrent.
 
     var allowed = (infoHash === 'aaa67059ed6bd08362da625b3ae77f6f4a075aaa')
-    cb(allowed)
-
-    // In addition to returning a boolean (`true` for allowed, `false` for disallowed),
-    // you can return an `Error` object to disallow and provide a custom reason.
+    if (allowed) {
+      // If the callback is passed `null`, the torrent will be allowed.
+      cb(null)
+    } else {
+      // If the callback is passed an `Error` object, the torrent will be disallowed
+      // and the error's `message` property will be given as the reason.
+      cb(new Error('disallowed torrent'))
+    }
   }
 })
 
diff --git a/server.js b/server.js
index 8548786..3723516 100644
--- a/server.js
+++ b/server.js
@@ -661,11 +661,10 @@ Server.prototype._onAnnounce = function (params, cb) {
 
   function createSwarm () {
     if (self._filter) {
-      self._filter(params.info_hash, params, function (allowed) {
-        if (allowed instanceof Error) {
-          cb(allowed)
-        } else if (!allowed) {
-          cb(new Error('disallowed info_hash'))
+      self._filter(params.info_hash, params, function (err) {
+        // Precense of err means that this info_hash is disallowed
+        if (err) {
+          cb(err)
         } else {
           self.createSwarm(params.info_hash, function (err, swarm) {
             if (err) return cb(err)
diff --git a/test/filter.js b/test/filter.js
index ffdd567..8eb4dd8 100644
--- a/test/filter.js
+++ b/test/filter.js
@@ -12,7 +12,11 @@ function testFilterOption (t, serverType) {
   var opts = { serverType: serverType } // this is test-suite-only option
   opts.filter = function (infoHash, params, cb) {
     process.nextTick(function () {
-      cb(infoHash !== fixtures.alice.parsedTorrent.infoHash)
+      if (infoHash === fixtures.alice.parsedTorrent.infoHash) {
+        cb(new Error('disallowed info_hash (Alice)'))
+      } else {
+        cb(null)
+      }
     })
   }
 
@@ -29,7 +33,7 @@ function testFilterOption (t, serverType) {
     if (serverType === 'ws') common.mockWebsocketTracker(client1)
 
     client1.once('warning', function (err) {
-      t.ok(/disallowed info_hash/.test(err.message), 'got client warning')
+      t.ok(err.message.includes('disallowed info_hash (Alice)'), 'got client warning')
 
       client1.destroy(function () {
         t.pass('client1 destroyed')
@@ -62,7 +66,7 @@ function testFilterOption (t, serverType) {
 
     server.removeAllListeners('warning')
     server.once('warning', function (err) {
-      t.ok(/disallowed info_hash/.test(err.message), 'got server warning')
+      t.ok(err.message.includes('disallowed info_hash (Alice)'), 'got server warning')
       t.equal(Object.keys(server.torrents).length, 0)
     })
 
@@ -88,8 +92,11 @@ function testFilterCustomError (t, serverType) {
   var opts = { serverType: serverType } // this is test-suite-only option
   opts.filter = function (infoHash, params, cb) {
     process.nextTick(function () {
-      if (infoHash === fixtures.alice.parsedTorrent.infoHash) cb(new Error('alice blocked'))
-      else cb(true)
+      if (infoHash === fixtures.alice.parsedTorrent.infoHash) {
+        cb(new Error('alice blocked'))
+      } else {
+        cb(null)
+      }
     })
   }