--- a/browser/components/sessionstore/src/TabStateCache.jsm
+++ b/browser/components/sessionstore/src/TabStateCache.jsm
@@ -290,22 +290,18 @@ let TabStateCacheInternal = {
    *        The new data to be stored for the given |browser|.
    */
   updatePersistent: function (browser, newData) {
     let data = this._persistentData.get(browser) || {};
 
     for (let key of Object.keys(newData)) {
       let value = newData[key];
       if (value === null) {
-        // Remove the field if the value is null.
-        this.removeField(browser, key);
         delete data[key];
       } else {
-        // Update the field otherwise.
-        this.updateField(browser, key, value);
         data[key] = value;
       }
     }
 
     this._persistentData.set(browser, data);
   },
 
   _normalizeToBrowser: function(aKey) {