diff --git a/tests/cli/test_repair.py b/tests/cli/test_repair.py
index 37a69a2..f91a769 100644
--- a/tests/cli/test_repair.py
+++ b/tests/cli/test_repair.py
@@ -23,6 +23,16 @@ def test_repair_uids():
     assert uid1 != uid2
 
 
+def test_repair_nonascii_uids():
+    s = MemoryStorage()
+    href, etag = s.upload(Item(u'BEGIN:VCARD\nUID:äää\nEND:VCARD'))
+    assert s.get(href)[0].uid == u'äää'
+    repair_storage(s)
+    newuid = s.get(href)[0].uid
+    assert newuid != u'äää'
+    assert newuid.encode('ascii', 'ignore').decode('ascii') == newuid
+
+
 def test_full(tmpdir, runner):
     runner.write_with_general(dedent('''
         [storage foo]
diff --git a/vdirsyncer/cli/utils.py b/vdirsyncer/cli/utils.py
index 21f2f41..d168f84 100644
--- a/vdirsyncer/cli/utils.py
+++ b/vdirsyncer/cli/utils.py
@@ -676,27 +676,38 @@ def repair_storage(storage):
                                .format(href))
             continue
 
-        if item.uid is None or item.uid in seen_uids:
-            if item.uid is None:
-                cli_logger.warning('No UID, assigning random one.')
-            else:
-                cli_logger.warning('Duplicate UID, reassigning random one.')
-
-            new_uid = uuid.uuid4()
-            stack = [parsed]
-            while stack:
-                component = stack.pop()
-                if component.name in ('VEVENT', 'VTODO', 'VJOURNAL', 'VCARD'):
-                    component['UID'] = new_uid
-                    changed = True
-                else:
-                    stack.extend(component.subcomponents)
+        if item.uid is None:
+            cli_logger.warning('No UID, assigning random one.')
+            changed = reroll_uid(parsed) or changed
+        elif item.uid in seen_uids:
+            cli_logger.warning('Duplicate UID, assigning random one.')
+            changed = reroll_uid(parsed) or changed
+        elif item.uid.encode('ascii', 'ignore').decode('ascii') != item.uid:
+            cli_logger.warning('UID is non-ascii, assigning, random one.')
+            changed = reroll_uid(parsed) or changed
 
         new_item = Item(u'\r\n'.join(parsed.dump_lines()))
         assert new_item.uid
         seen_uids.add(new_item.uid)
         if changed:
-            storage.update(href, new_item, etag)
+            try:
+                storage.update(href, new_item, etag)
+            except Exception:
+                cli_logger.exception('Server rejected new item.')
+
+
+def reroll_uid(component):
+    new_uid = uuid.uuid4()
+    stack = [component]
+    changed = False
+    while stack:
+        component = stack.pop()
+        if component.name in ('VEVENT', 'VTODO', 'VJOURNAL', 'VCARD'):
+            component['UID'] = new_uid
+            changed = True
+        else:
+            stack.extend(component.subcomponents)
+    return changed
 
 
 def assert_permissions(path, wanted):