candidates := set.CreateStringSet(subSysEnvVars...)

	// Remove all default target env vars from the candidates set (as they
	// are valid).
	for _, param := range validKeys {
		paramEnvName := getEnvVarName(subSys, Default, param)
		candidates.Remove(paramEnvName)
	}

	isSingleTarget := SubSystemsSingleTargets.Contains(subSys)
	if isSingleTarget && len(candidates) > 0 {