diff --git a/browser/components/sessionstore/src/SessionStore.jsm b/browser/components/sessionstore/src/SessionStore.jsm
index 5a00b61a18f4..83da80cc6606 100644
--- a/browser/components/sessionstore/src/SessionStore.jsm
+++ b/browser/components/sessionstore/src/SessionStore.jsm
@@ -485,8 +485,6 @@ let SessionStoreInternal = {
         this._prefBranch.getBoolPref("sessionstore.resume_session_once"))
       this._prefBranch.setBoolPref("sessionstore.resume_session_once", false);
 
-    this._initEncoding();
-
     this._performUpgradeBackup();
 
     this._sessionInitialized = true;
@@ -521,13 +519,6 @@ let SessionStoreInternal = {
     }.bind(this));
   },
 
-  _initEncoding : function ssi_initEncoding() {
-    // The (UTF-8) encoder used to write to files.
-    XPCOMUtils.defineLazyGetter(this, "_writeFileEncoder", function () {
-      return new TextEncoder();
-    });
-  },
-
   _initPrefs : function() {
     this._prefBranch = Services.prefs.getBranch("browser.");