diff --git a/examples/callback-example.creek b/examples/callback-example.creek
new file mode 100644
index 0000000..7438f80
--- /dev/null
+++ b/examples/callback-example.creek
@@ -0,0 +1,12 @@
+creek = require('../lib/creek')
+
+agg = creek.compoundAggregator.create()
+
+agg.track('sum', aggregator: creek.aggregators.sum.alltime, field: 'i')
+agg.track('count', aggregator: creek.aggregators.count.alltime, field: 'i')
+
+agg.on 'change', (newValue, oldValue, name) -> console.log(name, newValue, oldValue)
+
+agg.push(new Date(), i:1)
+agg.push(new Date(), i:3)
+
diff --git a/examples/twitter.creek b/examples/twitter.creek
index bf2a853..252e757 100644
--- a/examples/twitter.creek
+++ b/examples/twitter.creek
@@ -9,7 +9,7 @@ track 'popular-words',
   aggregator: popular.timeboxed
   field: (o) -> if o.text then o.text.toLowerCase().split(' ') else undefined
   period: 60
-  precision: 5
+  precision: 1
   top: 10
   keep: 5
   before: (v) -> if v and v.length > 4 then v else undefined
@@ -18,6 +18,6 @@ track 'popular-urls',
   aggregator: popular.timeboxed
   field: (o) -> if o.text then o.text.split(' ') else undefined
   period: 60*30
-  precision: 60
+  precision: 10
   top: 5
   before: (v) -> if v and v.indexOf('http://') is 0 then v else undefined
\ No newline at end of file
diff --git a/lib/compound-aggregator.coffee b/lib/compound-aggregator.coffee
index 3663810..ad95da7 100644
--- a/lib/compound-aggregator.coffee
+++ b/lib/compound-aggregator.coffee
@@ -13,9 +13,10 @@ class CompoundAggregator
     if arguments.length == 3
       @aggregators[name].aggregator.on(event, callback)
     else
-      event = name
       callback = event
-      agg.aggregator.on(event, callback) for name, agg of @aggregators
+      event = name
+      for name, agg of @aggregators
+        ((name) -> agg.aggregator.on(event, (newValue, oldValue) -> callback(newValue, oldValue, name)))(name)
   push: (time, obj) ->
     for name, agg of @aggregators
       val = agg.getValue(obj)
diff --git a/package.json b/package.json
index 3a72aea..ffd5792 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "creek",
   "description": "Configurable stream aggregator",
-  "version": "0.2.2",
+  "version": "0.2.4",
   "author": {
     "name": "Andy Kent",
     "email": "andy@forward.co.uk"