diff --git a/Changelog.rst b/Changelog.rst
index 0064681..5e9be44 100644
--- a/Changelog.rst
+++ b/Changelog.rst
@@ -7,6 +7,8 @@ ChangeLog
 WIP (add new stuff for the next release)
 ========================================
 
+* Avoid lockups for IMAP synchronizations running with the
+  "-1" command-line switch (X-Ryl669 <boite.pour.spam@gmail.com>)
 * Dump stacktrace for all threads on SIGQUIT: ease debugging
   of threading and other issues
 * SIGHUP is now handled as the termination notification rather than
diff --git a/offlineimap/accounts.py b/offlineimap/accounts.py
index dd65842..88d62d8 100644
--- a/offlineimap/accounts.py
+++ b/offlineimap/accounts.py
@@ -321,13 +321,16 @@ class SyncableAccount(Account):
                     self.ui.debug('', "Not syncing filtered folder '%s'"
                                  "[%s]" % (localfolder, localfolder.repository))
                     continue # Ignore filtered folder
-                thread = InstanceLimitedThread(\
-                    instancename = 'FOLDER_' + self.remoterepos.getname(),
-                    target = syncfolder,
-                    name = "Folder %s [acc: %s]" % (remotefolder, self),
-                    args = (self, remotefolder, quick))
-                thread.start()
-                folderthreads.append(thread)
+                if self.config.get('general', 'single-thread') == 'False':
+                    thread = InstanceLimitedThread(\
+                        instancename = 'FOLDER_' + self.remoterepos.getname(),
+                        target = syncfolder,
+                        name = "Folder %s [acc: %s]" % (remotefolder, self),
+                        args = (self, remotefolder, quick))
+                    thread.start()
+                    folderthreads.append(thread)
+                else:
+                    syncfolder(self, remotefolder, quick)
             # wait for all threads to finish
             for thr in folderthreads:
                 thr.join()
@@ -372,8 +375,7 @@ class SyncableAccount(Account):
             self.ui.error(e, exc_info()[2], msg = "Calling hook")
 
 def syncfolder(account, remotefolder, quick):
-    """This function is called as target for the
-    InstanceLimitedThread invokation in SyncableAccount.
+    """Synchronizes given remote folder for the specified account.
 
     Filtered folders on the remote side will not invoke this function."""
     remoterepos = account.remoterepos
diff --git a/offlineimap/folder/Base.py b/offlineimap/folder/Base.py
index c132713..e330086 100644
--- a/offlineimap/folder/Base.py
+++ b/offlineimap/folder/Base.py
@@ -403,7 +403,7 @@ class BaseFolder(object):
                 break
             self.ui.copyingmessage(uid, num+1, num_to_copy, self, dstfolder)
             # exceptions are caught in copymessageto()
-            if self.suggeststhreads():
+            if self.suggeststhreads() and self.config.get('general', 'single-thread') == 'False':
                 self.waitforthread()
                 thread = threadutil.InstanceLimitedThread(\
                     self.getcopyinstancelimit(),
diff --git a/offlineimap/init.py b/offlineimap/init.py
index e93a382..d25d7fa 100644
--- a/offlineimap/init.py
+++ b/offlineimap/init.py
@@ -251,6 +251,9 @@ class OfflineImap:
                 if type.lower() == 'imap':
                     imaplib.Debug = 5
 
+        # XXX: can we avoid introducing fake configuration item?
+        config.set_if_not_exists('general', 'single-thread', 'True' if options.singlethreading else 'False')
+
         if options.runonce:
             # FIXME: maybe need a better
             for section in accounts.getaccountlist(config):
diff --git a/offlineimap/threadutil.py b/offlineimap/threadutil.py
index a29e68f..33dbd64 100644
--- a/offlineimap/threadutil.py
+++ b/offlineimap/threadutil.py
@@ -39,6 +39,8 @@ def semaphorereset(semaphore, originalstate):
         semaphore.release()
 
 class threadlist:
+    """Store the list of all threads in the software so it can be used to find out
+    what's running and what's not."""
     def __init__(self):
         self.lock = Lock()
         self.list = []