jackc/pgx · error

invalid protocol version

Error message

invalid protocol version: %q

What it means

The protocol_version connection parameter was not one of the accepted values. Valid values are "3.0", "3.2", and "latest" (empty defaults to 3.0). The %q shows the rejected input.

Solutions

1. Set protocol_version to "3.0", "3.2", or "latest"
2. Remove the parameter to use the default (3.0)
3. Check for typos in the connection string

When it happens

Trigger: Thrown at pgconn/config.go:1117 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of jackc/pgx@ec1a0befd2 (2026-08-04). Data as JSON: /api/errors/8c48c4656e020ae2. Report an issue: GitHub.

Appendix: source

Thrown at pgconn/config.go:1117

	if err != nil {
		return err
	}

	if string(result[0].Rows[0][0]) != "t" {
		return &NotPreferredError{err: errors.New("server is not in hot standby mode")}
	}

	return nil
}

func parseProtocolVersion(s string) (uint32, error) {
	switch s {
	case "", "3.0":
		return pgproto3.ProtocolVersion30, nil
	case "3.2", "latest":
		return pgproto3.ProtocolVersion32, nil
	default:
		return 0, fmt.Errorf("invalid protocol version: %q", s)
	}
}

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