我在Postgres 11.4中工作。我有一个带有jsonb列的表：

Table "public.feature_bundle_plan_feature"
      Column       |            Type             | Collation | Nullable |    Default    
-------------------+-----------------------------+-----------+----------+---------------
 plan_feature_id   | integer                     |           | not null | 
 feature_bundle_id | integer                     |           | not null | 
 value             | jsonb                       |           |          | 'true'::jsonb

我可以像这样直接在jsonb value列中存储对象：

insert into feature_bundle_plan_feature(plan_feature_id, feature_bundle_id, value)
   values(1, 1, '{"foo":"bar"}');

但是，我似乎无法在CASE语句中执行相同的操作：

update feature_bundle_plan_feature set value = case
   when feature_bundle_id=1 then '{"foo":"bar"}'
   end;

失败原因：

ERROR:  column "value" is of type jsonb but expression is of type text
LINE 1: update feature_bundle_plan_feature set value = case                                         
HINT:  You will need to rewrite or cast the expression.

我做错了什么？