diff --git a/firefox_webextension/options.js b/firefox_webextension/options.js
index f3f24f2..a4a7e4b 100644
--- a/firefox_webextension/options.js
+++ b/firefox_webextension/options.js
@@ -1,13 +1,16 @@
 var default_preferences = {"pbkdf2_level": 1000,
-			   "account_url": "https://gpass-demo.soutade.fr/demo"};
+			   "account_url": "https://gpass-demo.soutade.fr/demo",
+			   "crypto_v1_compatible": true};
 
 function save() {
     var account_url = document.getElementById('account_url').value;
     var pbkdf2 = document.getElementById('pbkdf2').value;
+    var crypto_v1_compatible = document.getElementById('crypto_v1_compatible').checked;
 
     browser.storage.local.set({
 	"account_url":account_url,
-	"pbkdf2_level":pbkdf2
+	"pbkdf2_level":pbkdf2,
+	"crypto_v1_compatible": crypto_v1_compatible,
     })
 	.then(function ok() { alert("Saved"); },
 	      function err() { alert("Cannot save your preferences");}
@@ -18,6 +21,7 @@ function restoreOptions()
 {
     document.getElementById('account_url').value = default_preferences['account_url'];
     document.getElementById('pbkdf2').value = default_preferences['pbkdf2_level'];
+    document.getElementById('crypto_v1_compatible').checked = default_preferences["crypto_v1_compatible"];
 
     browser.storage.local.get().then(
 	function(prefs)
@@ -27,6 +31,9 @@ function restoreOptions()
 
 	    if (prefs.hasOwnProperty("pbkdf2_level"))
 		document.getElementById('pbkdf2').value = prefs["pbkdf2_level"];
+
+	    if (prefs.hasOwnProperty("crypto_v1_compatible"))
+		document.getElementById('crypto_v1_compatible').checked = prefs["crypto_v1_compatible"];
 	}
     );
 }