--- a/toolkit/components/telemetry/TelemetryPing.js
+++ b/toolkit/components/telemetry/TelemetryPing.js
@@ -463,17 +463,17 @@ TelemetryPing.prototype = {
     let hsuccess = Telemetry.getHistogramById("TELEMETRY_SUCCESS");
 
     let url = server + submitPath;
     let request = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"]
                   .createInstance(Ci.nsIXMLHttpRequest);
     request.mozBackgroundRequest = true;
     request.open("POST", url, true);
     request.overrideMimeType("text/plain");
-    request.setRequestHeader("Content-Type", "application/json");
+    request.setRequestHeader("Content-Type", "application/json; charset=UTF-8");
 
     let startTime = new Date();
 
     function finishRequest(channel) {
       let success = false;
       try {
         success = channel.QueryInterface(Ci.nsIHttpChannel).requestSucceeded;
       } catch(e) {
@@ -481,19 +481,47 @@ TelemetryPing.prototype = {
       hsuccess.add(success);
       hping.add(new Date() - startTime);
       if (isTestPing)
         Services.obs.notifyObservers(null, "telemetry-test-xhr-complete", null);
     }
     request.addEventListener("error", function(aEvent) finishRequest(request.channel), false);
     request.addEventListener("load", function(aEvent) finishRequest(request.channel), false);
 
-    request.send(data.payload);
+    request.setRequestHeader("Content-Encoding", "gzip");
+    let payloadStream = Cc["@mozilla.org/io/string-input-stream;1"]
+                        .createInstance(Ci.nsIStringInputStream);
+    payloadStream.data = this.gzipCompressString(data.payload);
+    request.send(payloadStream);
   },
-  
+
+  gzipCompressString: function gzipCompressString(string) {
+    let observer = {
+      buffer: "",
+      onStreamComplete: function(loader, context, status, length, result) {
+	this.buffer = String.fromCharCode.apply(this, result);
+      }
+    };
+
+    let scs = Cc["@mozilla.org/streamConverters;1"]
+              .getService(Ci.nsIStreamConverterService);
+    let listener = Cc["@mozilla.org/network/stream-loader;1"]
+                  .createInstance(Ci.nsIStreamLoader);
+    listener.init(observer);
+    let converter = scs.asyncConvertData("uncompressed", "gzip",
+                                         listener, null);
+    let stringStream = Cc["@mozilla.org/io/string-input-stream;1"]
+                       .createInstance(Ci.nsIStringInputStream);
+    stringStream.data = string;
+    converter.onStartRequest(null, null);
+    converter.onDataAvailable(null, null, stringStream, 0, string.length);
+    converter.onStopRequest(null, null, null);
+    return observer.buffer;
+  },
+
   attachObservers: function attachObservers() {
     if (!this._initialized)
       return;
     Services.obs.addObserver(this, "cycle-collector-begin", false);
     Services.obs.addObserver(this, "idle-daily", false);
   },
 
   detachObservers: function detachObservers() {

--- a/toolkit/components/telemetry/tests/unit/test_TelemetryPing.js
+++ b/toolkit/components/telemetry/tests/unit/test_TelemetryPing.js
@@ -52,18 +52,41 @@ function telemetryObserver(aSubject, aTo
   Services.startup.interrupted = true;
   telemetry_ping();
 }
 
 function checkHistograms(request, response) {
   // do not need the http server anymore
   httpserver.stop(do_test_finished);
   let s = request.bodyInputStream;
-  let payload = Cc["@mozilla.org/dom/json;1"].createInstance(Ci.nsIJSON)
-                                             .decodeFromStream(s, s.available());
+  let payload = null;
+  let decoder = Cc["@mozilla.org/dom/json;1"].createInstance(Ci.nsIJSON)
+
+  if (request.getHeader("content-encoding") == "gzip") {
+    let observer = {
+      buffer: "",
+      onStreamComplete: function(loader, context, status, length, result) {
+	this.buffer = String.fromCharCode.apply(this, result);
+      }
+    };
+
+    let scs = Cc["@mozilla.org/streamConverters;1"]
+              .getService(Ci.nsIStreamConverterService);
+    let listener = Cc["@mozilla.org/network/stream-loader;1"]
+                  .createInstance(Ci.nsIStreamLoader);
+    listener.init(observer);
+    let converter = scs.asyncConvertData("gzip", "uncompressed",
+                                         listener, null);
+    converter.onStartRequest(null, null);
+    converter.onDataAvailable(null, null, s, 0, s.available());
+    converter.onStopRequest(null, null, null);
+    payload = decoder.decode(observer.buffer);
+  } else {
+    payload = decoder.decodeFromStream(s, s.available());
+  }
 
   do_check_eq(request.getHeader("content-type"), "application/json; charset=UTF-8");
   do_check_true(payload.simpleMeasurements.uptime >= 0);
   do_check_true(payload.simpleMeasurements.startupInterrupted === 1);
   // get rid of the non-deterministic field
   const expected_info = {
     reason: "test-ping",
     OS: "XPCShell",