--- a/calendar/base/modules/utils/calAuthUtils.jsm
+++ b/calendar/base/modules/utils/calAuthUtils.jsm
@@ -218,17 +218,21 @@ var calauth = {
      * require it. This is a fallback for compatibility only and should be removed a few versions
      * after Lightning 6.2
      *
      * @param {String} aOrigin      The hostname or origin to check
      * @return {String}             The origin uri
      */
     _ensureOrigin: function(aOrigin) {
         try {
-            return Services.io.newURI(aOrigin).prePath;
+            let {prePath, spec} = Services.io.newURI(aOrigin);
+            if (prePath == "oauth:") {
+                return spec;
+            }
+            return prePath;
         } catch (e) {
             return "https://" + aOrigin;
         }
     },
 
     /**
      * Helper to insert/update an entry to the password manager.
      *