diff --git a/lib/altimeter.js b/lib/altimeter.js
index d09d12c4e..a33f9246c 100644
--- a/lib/altimeter.js
+++ b/lib/altimeter.js
@@ -86,11 +86,11 @@ function Altimeter(opts) {
     data.m = data.meters = this.meters;
     data.ft = data.feet = this.feet;
 
-    this.emit("data", null, data);
+    this.emit("data", data);
 
     if (this.meters !== last) {
       last = this.meters;
-      this.emit("change", null, data);
+      this.emit("change", data);
     }
   }.bind(this), freq);
 }