diff --git a/web-world/geolocation.rkt b/js/world/geo.rkt
similarity index 55%
rename from web-world/geolocation.rkt
rename to js/world/geo.rkt
index 4b303aa..59e28f1 100644
--- a/web-world/geolocation.rkt
+++ b/js/world/geo.rkt
@@ -1,6 +1,7 @@
-#lang s-exp "../lang/base.rkt"
-(require "../js/world.rkt"
-         "../js.rkt")
+#lang s-exp "../../lang/base.rkt"
+
+(require "../../js.rkt")
+(require "../../js/world.rkt")
 
 (provide on-geo)
 
@@ -8,8 +9,10 @@
   (js-function->procedure
    "function(locationCallback) {
         return navigator.geolocation.watchPosition(
-            function(evt) { locationCallback(plt.runtime.makeFloat(evt.latitude),
-                                             plt.runtime.makeFloat(evt.longitude)); })}"))
+            function(evt) {
+                var coords = evt.coords;
+                locationCallback(plt.runtime.makeFloat(coords.latitude),
+                                 plt.runtime.makeFloat(coords.longitude)); })}"))
 
 (define shutdown-geo
   (js-function->procedure
diff --git a/js/world/js-impl.js b/js/world/js-impl.js
index 22f5f96..0bbd61b 100644
--- a/js/world/js-impl.js
+++ b/js/world/js-impl.js
@@ -24,9 +24,12 @@
         var enabled = false;
         var fireEvent;
 
-        var sender = function(v) {
+        var sender = function() {
+            var args;
             if (enabled) {
-                fireEvent(void(0), v);
+                args = Array.prototype.slice.call(arguments, 0);
+                args.unshift(void(0));
+                fireEvent.apply(void(0), args);
             }
         };
 
@@ -75,11 +78,11 @@
             var shutdownProcedure = wrapFunction(checkProcedure(M, 'make-world-event-handler', 1));
             var eventSource = makeJsEventSource(setupProcedure, shutdownProcedure);
             var makeHandler = makePrimitiveProcedure(
-                'make-js-world-event',
+                'world-event-handler',
                 1,
                 function(M) {
-                    var onEvent = wrapFunction(checkProcedure(M, 'js-world-event-handler', 0));
-                    return new EventHandler('js-world-event', eventSource, onEvent);
+                    var onEvent = wrapFunction(checkProcedure(M, 'world-event-handler', 0));
+                    return new EventHandler('world-event-handler', eventSource, onEvent);
                 });
             finalizeClosureCall(M, makeHandler);
         });
diff --git a/js/world/test-geo.rkt b/js/world/test-geo.rkt
new file mode 100644
index 0000000..ac593fa
--- /dev/null
+++ b/js/world/test-geo.rkt
@@ -0,0 +1,9 @@
+#lang planet dyoo/whalesong
+
+(require (planet dyoo/whalesong/web-world)
+         "geo.rkt")
+
+
+(big-bang (list 'undefined 'undefined)
+          (on-geo (lambda (w v lat lng)
+                    (list lat lng))))
\ No newline at end of file
diff --git a/web-world/js-impl.js b/web-world/js-impl.js
index d8be353..098e31e 100644
--- a/web-world/js-impl.js
+++ b/web-world/js-impl.js
@@ -16,7 +16,7 @@
     var makeList = plt.baselib.lists.makeList;
     var makePair = plt.baselib.lists.makePair;
     var makeSymbol = plt.baselib.symbols.makeSymbol;
-
+    var isArityMatching = plt.baselib.arity.isArityMatching;
 
 
     // EventHandler and the other classes here will be defined below.
@@ -1258,7 +1258,7 @@
                 // Apply all the events on the queue, call toDraw, and then stop.
                 // If the world ever satisfies stopWhen, stop immediately and quit.
                 var nextEvent;
-                var data;
+                var args;
                 var racketWorldCallback;
                 var mockView;
                 dispatchingEvents = true;
@@ -1271,9 +1271,8 @@
                         mockView = mockView.updateFocus(nextEvent.who.id);
                     }
 
-                    // FIXME: deal with event data here
                     racketWorldCallback = nextEvent.handler.racketWorldCallback;
-                    data = nextEvent.data[0];
+                    args = nextEvent.data.slice(0);
                     var onGoodWorldUpdate = 
                         function(newWorld) {
                             world = newWorld;
@@ -1290,19 +1289,22 @@
                                      },
                                      fail);
                         };
-                    if (plt.baselib.arity.isArityMatching(racketWorldCallback.racketArity, 3)) {
+                    if (isArityMatching(racketWorldCallback.racketArity, 1)) {
+                        racketWorldCallback(internalCall, 
+                                            world,
+                                            onGoodWorldUpdate,
+                                            fail);
+                    } else if (isArityMatching(racketWorldCallback.racketArity, 2)) {
                         racketWorldCallback(internalCall, 
                                             world,
                                             mockView,
-                                            data,
                                             onGoodWorldUpdate,
                                             fail);
                     } else {
-                        racketWorldCallback(internalCall, 
-                                            world,
-                                            mockView,
-                                            onGoodWorldUpdate,
-                                            fail);
+                        args = ([internalCall, world, mockView]
+                                .concat(args)
+                                .concat([onGoodWorldUpdate, fail]));
+                        racketWorldCallback.apply(null, args);
                     }
                 } else {
                     dispatchingEvents = false;