AddHttpsCertificate command "wrong filename"error | Telit Cinterion IoT Developer Community

I'm trying to generate the command to add a certificate to a EHS6 module, but  jseccmd.jar always gives me an error for the command  "AddHttpsCertificate" command (as per documentation). All other commands work fine and don't give error.

So if I execute the following command:

java -jar jseccmd.jar -cmd AddHttpsCertificate -imei [my_imei number] -alias operator -storepass keystorepass -keypass keypass -keystore ks/testchain.ks -filename mca.der > mca.bin

I always get the error:

wrong filename: mca.der

I get the error for whatever file I put for the -filename argument. 

The mca.der is a CA root certificate for the certificate of the server I'm trying to connect to.