Can't update queryset after Count annotation

[Fraser Harris]

Query:

>>> Category.objects.annotate(Count('tiles')).update(name='foo')
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/opt/secondfunnel/venv/local/lib/python2.7/site-packages/django/db/models/query.py", line 490, in update
    rows = query.get_compiler(self.db).execute_sql(None)
  File "/opt/secondfunnel/venv/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 976, in execute_sql
    cursor = super(SQLUpdateCompiler, self).execute_sql(result_type)
  File "/opt/secondfunnel/venv/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 782, in execute_sql
    cursor.execute(sql, params)
  File "/opt/secondfunnel/venv/local/lib/python2.7/site-packages/django/db/backends/util.py", line 69, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/opt/secondfunnel/venv/local/lib/python2.7/site-packages/django/db/backends/util.py", line 53, in execute
    return self.cursor.execute(sql, params)
  File "/opt/secondfunnel/venv/local/lib/python2.7/site-packages/django/db/utils.py", line 99, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/opt/secondfunnel/venv/local/lib/python2.7/site-packages/django/db/backends/util.py", line 53, in execute
    return self.cursor.execute(sql, params)
ProgrammingError: subquery has too many columns
LINE 1: ..." SET "name" = 'foo' WHERE "assets_category"."id" IN (SELECT...
                                                             ^

Models:

class Category(BaseModel):
    tiles = models.ManyToManyField(Tile, related_name='categories')
    name = models.CharField(max_length=255)

class Tile(Model):
    pass

SQL Query from django.db.connections.queries:

UPDATE "assets_category" SET "name" = \'foo\' WHERE "assets_category"."id" IN (SELECT U0."id", COUNT(U2."tile_id") AS "tiles__count" FROM "assets_category" U0 LEFT OUTER JOIN "assets_category_tiles" U2 ON ( U0."id" = U2."category_id" ) GROUP BY U0."id", U0."name")