diff --git a/toolkit/components/telemetry/TelemetryPing.js b/toolkit/components/telemetry/TelemetryPing.js
index 003ef5c23135..8572067ed0bf 100644
--- a/toolkit/components/telemetry/TelemetryPing.js
+++ b/toolkit/components/telemetry/TelemetryPing.js
@@ -1015,9 +1015,6 @@ TelemetryPing.prototype = {
         this._isIdleObserver = true;
       }).bind(this), Ci.nsIThread.DISPATCH_NORMAL);
       break;
-    case "test-save-histograms":
-      this.saveHistograms(aSubject.QueryInterface(Ci.nsIFile), aData != "async");
-      break;
     case "test-load-histograms":
       this._pingsLoaded = 0;
       this._pingLoadsCompleted = 0;
diff --git a/toolkit/components/telemetry/nsITelemetryPing.idl b/toolkit/components/telemetry/nsITelemetryPing.idl
index 3fde75c18b91..d5e4081cc72e 100644
--- a/toolkit/components/telemetry/nsITelemetryPing.idl
+++ b/toolkit/components/telemetry/nsITelemetryPing.idl
@@ -5,7 +5,10 @@
 
 #include "nsIObserver.idl"
 
+interface nsIFile;
+
 [scriptable, uuid(077ee790-3a9d-11e2-81c1-0800200c9a66)]
 interface nsITelemetryPing : nsIObserver {
   jsval getPayload();
+  void saveHistograms(in nsIFile aFile, in boolean aSync);
 };
diff --git a/toolkit/components/telemetry/tests/unit/test_TelemetryPing.js b/toolkit/components/telemetry/tests/unit/test_TelemetryPing.js
index 26c18dd35364..47b2529e0221 100644
--- a/toolkit/components/telemetry/tests/unit/test_TelemetryPing.js
+++ b/toolkit/components/telemetry/tests/unit/test_TelemetryPing.js
@@ -100,7 +100,7 @@ function telemetryObserver(aSubject, aTopic, aData) {
   setupTestData();
 
   const TelemetryPing = Cc["@mozilla.org/base/telemetry-ping;1"].getService(Ci.nsITelemetryPing);
-  TelemetryPing.observe(histogramsFile, "test-save-histograms", null);
+  TelemetryPing.saveHistograms(histogramsFile, true);
   TelemetryPing.observe(histogramsFile, "test-load-histograms", null);
   telemetry_ping();
 }
@@ -288,7 +288,7 @@ function runAsyncTestObserver(aSubject, aTopic, aData) {
 
     TelemetryPing.observe(histogramsFile, "test-load-histograms", "async");
   }, "telemetry-test-save-complete", false);
-  TelemetryPing.observe(histogramsFile, "test-save-histograms", "async");
+  TelemetryPing.saveHistograms(histogramsFile, false);
 }
 
 function checkPersistedHistogramsAsync(request, response) {
@@ -322,7 +322,7 @@ function runInvalidJSONTest() {
 function runOldPingFileTest() {
   let histogramsFile = getSavedHistogramsFile("old-histograms.dat");
   const TelemetryPing = Cc["@mozilla.org/base/telemetry-ping;1"].getService(Ci.nsITelemetryPing);
-  TelemetryPing.observe(histogramsFile, "test-save-histograms", null);
+  TelemetryPing.saveHistograms(histogramsFile, true);
   do_check_true(histogramsFile.exists());
 
   let mtime = histogramsFile.lastModifiedTime;