Schema Registry: Error when registering schema with references

Schema Registry
1

I am following the example provided in the document about registering schemas with references: Schema Registry API Reference | Confluent Documentation

First, I register a string schema under the subject hello:

curl -X POST "http://localhost:8087/subjects/hello/versions" \
     -H "Content-Type: application/json" \
     -d '{ "schema": "{\"type\":\"string\"}"}’
}'

Next, I register the following schema alongside the references:

curl -X POST "http://localhost:8087/subjects/foo/versions" \
     -H "Content-Type: application/json" \
     -d '{
       "schema": "{\"type\":\"record\",\"name\":\"test\",\"fields\":[{\"name\":\"f1\",\"type\":\"string\"},{\"name\":\"f2\",\"type\":\"com.acme.Referenced\"}]}",
       "references": [
         {
           "name": "com.acme.Referenced",
           "subject": "hello",
           "version": 1
         }
       ]
     }'

However, I get the following error: "com.acme.Referenced\" is not a defined name. The type of the \"f2\" field must be a defined name or a {\"type\": ...} expression."}.

Any chance anyone know what is the cause of this error?