diff --git a/extensions/firefox/content/PdfJsTelemetry-stub.jsm b/extensions/firefox/content/PdfJsTelemetry-stub.jsm
index 047941dfe..69f4a1844 100644
--- a/extensions/firefox/content/PdfJsTelemetry-stub.jsm
+++ b/extensions/firefox/content/PdfJsTelemetry-stub.jsm
@@ -15,9 +15,9 @@
 
 "use strict";
 
-this.EXPORTED_SYMBOLS = ["PdfJsTelemetry"];
+var EXPORTED_SYMBOLS = ["PdfJsTelemetry"];
 
-this.PdfJsTelemetry = {
+var PdfJsTelemetry = {
   onViewerIsUsed() {
   },
   onFallback() {
diff --git a/extensions/firefox/content/PdfJsTelemetry.jsm b/extensions/firefox/content/PdfJsTelemetry.jsm
index 4fc6efe76..0436debd2 100644
--- a/extensions/firefox/content/PdfJsTelemetry.jsm
+++ b/extensions/firefox/content/PdfJsTelemetry.jsm
@@ -16,11 +16,11 @@
 
 "use strict";
 
-this.EXPORTED_SYMBOLS = ["PdfJsTelemetry"];
+var EXPORTED_SYMBOLS = ["PdfJsTelemetry"];
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 
-this.PdfJsTelemetry = {
+var PdfJsTelemetry = {
   onViewerIsUsed() {
     let histogram = Services.telemetry.getHistogramById("PDF_VIEWER_USED");
     histogram.add(true);