CouchDB replication error: {"error":"bad_content_type","reason":"Content-Type must be application/json"}

I'm trying to use the replication in CouchDB.

When I enter the following code :

 curl -X POST http://127.0.0.1:5984/_replicate \
-d ’{"source":"musica","target":"musica-replica"}’

I receive the following error:

{"error":"bad_content_type","reason":"Content-Type must be application/json"}

Can you help me?