diff --git a/reserve.txt b/reserve.txt
index f3a36ba..ed79547 100644
--- a/reserve.txt
+++ b/reserve.txt
@@ -39,4 +39,5 @@ memoizedProps
 props
 children
 channel
-messages
\ No newline at end of file
+messages
+msSaveBlob
\ No newline at end of file
diff --git a/src/tracker/dom.js b/src/tracker/dom.js
index a1ac22c..d355c55 100644
--- a/src/tracker/dom.js
+++ b/src/tracker/dom.js
@@ -65,7 +65,7 @@ var DOM = (function(){
     downloadTextFile: (fileName, fileContents) => {
       var blob = new Blob([fileContents], { "type": "octet/stream" });
       
-      if (window.navigator.msSaveBlob){
+      if ("msSaveBlob" in window.navigator){
         return window.navigator.msSaveBlob(blob, fileName);
       }