diff --git a/offlineimap.conf b/offlineimap.conf
index b57b182..7af2e7e 100644
--- a/offlineimap.conf
+++ b/offlineimap.conf
@@ -801,7 +801,7 @@ remoteuser = username
 # limitations, if GSSAPI is set, it will be tried first, no matter where it was
 # specified in the list.
 #
-#auth_mechanisms = GSSAPI, CRAM-MD5, XOAUTH2, PLAIN, LOGIN
+#auth_mechanisms = GSSAPI, XOAUTH2, CRAM-MD5, PLAIN, LOGIN
 
 
 # This option stands in the [Repository RemoteExample] section.
@@ -812,7 +812,9 @@ remoteuser = username
 # with type = IMAP for compatible servers.
 #
 # Mandatory parameters are "oauth2_client_id", "oauth2_client_secret" and
-# either "oauth2_refresh_token" or "oauth2_access_token".
+# either "oauth2_refresh_token" or "oauth2_access_token". XOAUTH2 mechanism
+# won't be tried if both oauth2_refresh_token and oauth2_access_token are not
+# set.
 #
 # See below to learn how to get those.
 #
diff --git a/offlineimap/repository/Gmail.py b/offlineimap/repository/Gmail.py
index a45d274..c7a0984 100644
--- a/offlineimap/repository/Gmail.py
+++ b/offlineimap/repository/Gmail.py
@@ -47,7 +47,7 @@ class GmailRepository(IMAPRepository):
         try:
             return super(GmailRepository, self).gethost()
         except OfflineImapError:
-            # nothing was configured, cache and return hardcoded one
+            # Nothing was configured, cache and return hardcoded one.
             self._host = GmailRepository.HOSTNAME
             return self._host
 
@@ -60,10 +60,10 @@ class GmailRepository(IMAPRepository):
         url = super(GmailRepository, self).getoauth2_request_url()
         if url is None:
             # Nothing was configured, cache and return hardcoded one.
-            self._oauth2_request_url = GmailRepository.OAUTH2_URL
+            self.setoauth2_request_url(GmailRepository.OAUTH2_URL)
         else:
-            self._oauth2_request_url = url
-        return self._oauth2_request_url
+            self.setoauth2_request_url(url)
+        return self.oauth2_request_url
 
     def getport(self):
         return GmailRepository.PORT
@@ -82,8 +82,8 @@ class GmailRepository(IMAPRepository):
         return folder.Gmail.GmailFolder
 
     def gettrashfolder(self, foldername):
-        #: Where deleted mail should be moved
-        return  self.getconf('trashfolder','[Gmail]/Trash')
+        # Where deleted mail should be moved
+        return self.getconf('trashfolder', '[Gmail]/Trash')
 
     def getspamfolder(self):
         #: Gmail also deletes messages upon EXPUNGE in the Spam folder
diff --git a/offlineimap/repository/IMAP.py b/offlineimap/repository/IMAP.py
index 17655d5..87d0dd4 100644
--- a/offlineimap/repository/IMAP.py
+++ b/offlineimap/repository/IMAP.py
@@ -36,11 +36,11 @@ class IMAPRepository(BaseRepository):
         BaseRepository.__init__(self, reposname, account)
         # self.ui is being set by the BaseRepository
         self._host = None
-        self._oauth2_request_url = None
+        # Must be set before calling imapserver.IMAPServer(self)
+        self.oauth2_request_url = None
         self.imapserver = imapserver.IMAPServer(self)
         self.folders = None
         self.copy_ignore_eval = None
-        self.oauth2_request_url = None
         # Keep alive.
         self.kaevent = None
         self.kathread = None
@@ -295,12 +295,15 @@ class IMAPRepository(BaseRepository):
         value = self.getconf('cert_fingerprint', "")
         return [f.strip().lower() for f in value.split(',') if f]
 
-    def getoauth2_request_url(self):
-        if self._oauth2_request_url:  # Use cached value if possible.
-            return self._oauth2_request_url
+    def setoauth2_request_url(self, url):
+        self.oauth2_request_url = url
 
-        self.oauth2_request_url = self.getconf('oauth2_request_url', None)
-        return self._oauth2_request_url
+    def getoauth2_request_url(self):
+        if self.oauth2_request_url is not None: # Use cached value if possible.
+            return self.oauth2_request_url
+
+        self.setoauth2_request_url(self.getconf('oauth2_request_url', None))
+        return self.oauth2_request_url
 
     def getoauth2_refresh_token(self):
         refresh_token = self.getconf('oauth2_refresh_token', None)