Copying config into image, error loading config at line 1:15 illegal char - but my config only has 11 lines?

[markpendlebury]

I'm attempting to build my own docker image based from vault:latest:

simple docker file:

FROM vault:latest
WORKDIR /vault
COPY config/vault.config config/vault.config
RUN chown vault:vault config/vault.config
ENTRYPOINT [ "vault server", " -config /vault/config/vault.config" ]

however when i run the image in a container i get:

error loading configuration from /vault/config/vault.config: At 1:15: illegal char

my config file is:

storage "file": {
    "path": "/vault/data"
}

listener "tcp" { 
  address     = "0.0.0.0:8200" 
  tls_disable = "true" 
}

api_addr = "http://0.0.0.0:8200"
ui = true

As you can see 11 lines NOT 15, so where is vault getting the illegal char from on line 15?

if i mount my local config as a volume and start vault in the same way it works successfully. Why is that?