diff --git a/browser/components/privatebrowsing/src/nsPrivateBrowsingService.js b/browser/components/privatebrowsing/src/nsPrivateBrowsingService.js
index e7cd108d0b4b..99fe1f88372d 100644
--- a/browser/components/privatebrowsing/src/nsPrivateBrowsingService.js
+++ b/browser/components/privatebrowsing/src/nsPrivateBrowsingService.js
@@ -466,6 +466,7 @@ PrivateBrowsingService.prototype = {
           if (this._autoStarted)
             aSubject.handleFlag("private", false);
 
+          Services.prefs.setBoolPref("browser.privatebrowsing.autostart", true);
           this.privateBrowsingEnabled = true;
           this._autoStarted = true;
           this._lastChangedByCommandLine = true;