diff --git a/firefox.nix b/firefox.nix
index 8f6db3b..0b1ce16 100644
--- a/firefox.nix
+++ b/firefox.nix
@@ -60,6 +60,7 @@ in
         DontCheckDefaultBrowser = true;
         PrimaryPassword = false;
         OfferToSaveLoginsDefault = false;
+        DisableBuiltinPDFViewer = true;
         PasswordManagerEnabled = false;
         DisableMasterPasswordCreation = true;
         AutofillAddressEnabled = false;
@@ -169,6 +170,7 @@ in
           "dom.security.https_only_mode" = true;
           "browser.privatebrowsing.autostart" = cfg.forcePrivateBrowsing;
           "extensions.activeThemeID" = "{2adf0361-e6d8-4b74-b3bc-3f450e8ebb69}";
+          "browser.sessionstore.resume_session_once" = !cfg.forcePrivateBrowsing;
         };
 
         search = {