diff --git a/js/source/source.js b/js/source/source.js
index 7d98b4d7fad..00f65e76d5b 100644
--- a/js/source/source.js
+++ b/js/source/source.js
@@ -10,6 +10,8 @@ var sourceTypes = {
     'image': require('../source/image_source')
 };
 
+var coreTypes = ['vector', 'raster', 'geojson', 'video', 'image'];
+
 /*
  * Creates a tiled data source instance given an options object.
  *
@@ -38,6 +40,16 @@ exports.setType = function (name, type) {
     sourceTypes[name] = type;
 };
 
+/**
+ * Returns the names of any registered non-core source types.
+ * @private
+ */
+exports.getCustomTypeNames = function () {
+    return Object.keys(sourceTypes).filter(function (type) {
+        return coreTypes.indexOf(type) < 0;
+    });
+};
+
 /**
  * The `Source` interface must be implemented by each source type, including "core" types (`vector`, `raster`, `video`, etc.) and all custom, third-party types.
  *
diff --git a/js/style/style.js b/js/style/style.js
index d16e1cbfd7d..8e821cbcbdb 100644
--- a/js/style/style.js
+++ b/js/style/style.js
@@ -1,5 +1,6 @@
 'use strict';
 
+var assert = require('assert');
 var Evented = require('../util/evented');
 var StyleLayer = require('./style_layer');
 var ImageSprite = require('./image_sprite');
@@ -70,11 +71,32 @@ function Style(stylesheet, animationLoop, workerCount) {
         this.fire('load');
     }.bind(this);
 
-    if (typeof stylesheet === 'string') {
-        ajax.getJSON(normalizeURL(stylesheet), stylesheetLoaded);
-    } else {
-        browser.frame(stylesheetLoaded.bind(this, null, stylesheet));
-    }
+    // register any existing custom source types with the workers
+    util.asyncAll(Source.getCustomTypeNames(), function (type, done) {
+        var CustomSource = Source.getType(type);
+        assert(CustomSource);
+
+        if (CustomSource.workerSourceURL) {
+            this.dispatcher.broadcast('load worker source', {
+                name: type,
+                url: CustomSource.workerSourceURL
+            }, done);
+        } else {
+            return done();
+        }
+    }.bind(this), function (err) {
+        if (err) {
+            this.fire('error', {error: err});
+            return;
+        }
+
+        if (typeof stylesheet === 'string') {
+            ajax.getJSON(normalizeURL(stylesheet), stylesheetLoaded);
+        } else {
+            browser.frame(stylesheetLoaded.bind(this, null, stylesheet));
+        }
+    }.bind(this));
+
 
     this.on('source.load', function(event) {
         var source = event.source;
diff --git a/test/js/style/style.test.js b/test/js/style/style.test.js
index 6e20250640d..d589bde5d76 100644
--- a/test/js/style/style.test.js
+++ b/test/js/style/style.test.js
@@ -131,6 +131,34 @@ test('Style', function(t) {
         });
     });
 
+    t.test('registers existing custom sources', function (t) {
+        function SourceType () {}
+        SourceType.workerSourceURL = 'worker-source.js';
+        function Dispatcher () {}
+        Dispatcher.prototype = {
+            broadcast: function (type, params, callback) {
+                if (type === 'load worker source') {
+                    t.equal(params.name, 'my-source-type');
+                    t.equal(params.url, 'worker-source.js');
+                    setTimeout(callback, 0);
+                }
+            }
+        };
+
+        t.plan(2);
+
+        var Style = proxyquire('../../../js/style/style', {
+            '../source/source': {
+                getType: function () { return SourceType; },
+                setType: function () {},
+                getCustomTypeNames: function () { return ['my-source-type']; }
+            },
+            '../util/dispatcher': Dispatcher
+        });
+
+        new Style(createStyleJSON());
+    });
+
     t.end();
 });
 
@@ -1184,11 +1212,12 @@ test('Style#addSourceType', function (t) {
     var Style = proxyquire('../../../js/style/style', {
         '../source/source': {
             getType: function (name) { return _types[name]; },
-            setType: function (name, create) { _types[name] = create; }
+            setType: function (name, create) { _types[name] = create; },
+            getTypeNames: function () { return []; }
         }
     });
 
-    t.test('adds factory function', function (t) {
+    t.test('adds source type', function (t) {
         var style = new Style(createStyleJSON());
         var SourceType = function () {};