gbt: Unable to setup prompt forwarding on macOS Mojave.

For a simple life I just want it working with SSH. I have:

# GBT Prompt forwarding
export GBT__HOME='/usr/local/share/gbt-git'
# Use 'md5' command instead of 'md5sum'
export GBT__SOURCE_MD5_LOCAL='md5'
# Cut the 4th field from the output of 'md5'
export GBT__SOURCE_MD5_CUT_LOCAL='4'
# Use 'gdate' instead of 'date'
export GBT__SOURCE_DATE='gdate'
# Use 'gdate' instead of 'date' (only if you run GBT on a Mac)
export GBT__SOURCE_BASE64_LOCAL='gbase64'
# List of plugins to pack for local commands
export GBT__PLUGINS_LOCAL='ssh'
source "$GBT__HOME/sources/gbts/cmd/local.sh"

alias ssh='gbt_ssh'

When running ‘ssh’ I get the error gbt_ssh:7: command not found: ssh: aliased to gbt_ssh. I believe this is because the gbt_ssh script calls ‘ssh’, which is aliased. Though I’m not even 50% on that.