parsing of "_" in json-file (proto definitions)?

[andife]

A message containing an "_" results in the following error:

PS C:\Dev> ghz --insecure --call com.api_pre.PreToHost.ReqPre -D .\req4.json localhost:5001
Error creating message from data. Data: '{
"image_md": {
"value": "03fdc668605146839ee31"
}
}' Error: json: cannot unmarshal object into Go value of type string

req4.json
{
"image_md": {
"value": "03fdc668605146839ee31"
}
}

Command line arguments / config
ghz --insecure --call com.api_pre.PreToHost.ReqPre -D .\req4.json localhost:5001

Environment

• OS: Windows10, powershell/cmd / gitbash
• ghz: ghz --version => dev => installed yesterday using "go install github.com/bojand/ghz/cmd/ghz@latest"

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Additional context
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