How to pass the fullname of a dependant chart into another chart in the values.yaml?

My values.yaml looks like this:

##
## Prisma chart configuration
##
prisma:
  enabled: true
  image:
    pullPolicy: Always
  auth:
    enabled: true
    secret: scret
  database:
    host: {{ template "postgresql.fullname" . }}
    port: 5432
    password: dbpass


##
## Postgreqsl chart configuration
##
postgresql:
  enabled: true
  imagePullPolicy: Always
  postgresqlUsername: prisma
  postgresqlPassword: dbpass
  persistence:
    enabled: true
    storageClass: storage-0

In there, I need to pass the name of the postgresql instance to prisma.

If I try to install this, it gives me the following error:

error converting YAML to JSON: yaml: invalid map key: map[interface {}]interface {}{"template \"postgresql.fullname\" .":interface {}(nil)}