Humanizr/Humanizer · error · ArgumentOutOfRangeException

Unknown byte-size unit system.

Error message

Unknown byte-size unit system.

What it means

Thrown by ByteSizeExtensions.HumanizeCompositeWithUnitSystem when the unitSystem argument is neither Legacy (which is handled earlier and delegates to HumanizeComposite) nor within the [DecimalSi, BinaryIec] range. The method explicitly rejects undefined enum values before doing any work.

Source

Thrown at src/Humanizer/Bytes/ByteSizeExtensions.cs:591

    /// <paramref name="unitSystem"/> is not defined or <paramref name="precision"/> is less than one.
    /// </exception>
    /// <exception cref="ArgumentNullException"><paramref name="separator"/> is <see langword="null"/>.</exception>
    public static string HumanizeCompositeWithUnitSystem(
        this ByteSize input,
        ByteSizeUnitSystem unitSystem,
        int precision = 2,
        IFormatProvider? formatProvider = null,
        string separator = " ",
        bool toWords = false)
    {
        if (unitSystem == ByteSizeUnitSystem.Legacy)
        {
            return input.HumanizeComposite(precision, formatProvider, separator, toWords);
        }

        if (unitSystem is < ByteSizeUnitSystem.DecimalSi or > ByteSizeUnitSystem.BinaryIec)
        {
            throw new ArgumentOutOfRangeException(nameof(unitSystem), unitSystem, "Unknown byte-size unit system.");
        }

        if (precision < 1)
        {
            throw new ArgumentOutOfRangeException(nameof(precision), precision, "Precision must be greater than zero.");
        }

        ArgumentNullException.ThrowIfNull(separator);
        formatProvider ??= CultureInfo.CurrentCulture;
        var culture = formatProvider as CultureInfo;
        if (culture is not null)
        {
            formatProvider = LocaleNumberFormattingOverrides.GetFormattingNumberFormat(culture);
        }

        var formatter = Configurator.GetFormatter(culture);
        var builtInFormatter = formatter as DefaultFormatter;
        if (builtInFormatter is not null &&

View on GitHub (pinned to ffc2b77c0f)

Solutions

1. Constrain the value to a named member before calling; map unknowns to Legacy.
2. Validate with Enum.IsDefined at the API boundary.
3. Use ByteSizeUnitSystem.DecimalSi or BinaryIec explicitly when the system is known.

Example fix

// before
var text = size.HumanizeCompositeWithUnitSystem((ByteSizeUnitSystem)configValue);

// after
var system = Enum.IsDefined(typeof(ByteSizeUnitSystem), configValue)
    ? (ByteSizeUnitSystem)configValue
    : ByteSizeUnitSystem.Legacy;
var text = size.HumanizeCompositeWithUnitSystem(system);

if (!Enum.IsDefined(typeof(ByteSizeUnitSystem), system))
    throw new ArgumentOutOfRangeException(nameof(system));

static bool IsSupportedSystem(ByteSizeUnitSystem s) =>
    s is ByteSizeUnitSystem.Legacy or ByteSizeUnitSystem.DecimalSi or ByteSizeUnitSystem.BinaryIec;

When it happens

Trigger: Calling HumanizeCompositeWithUnitSystem with an undefined ByteSizeUnitSystem value (e.g. (ByteSizeUnitSystem)42), or forwarding a config/JSON-derived integer that does not map to a named member.

Common situations: Deserializing the enum from a source with different naming, casting an arbitrary integer, or a binding default that produced an out-of-range value.

Related errors

• Unknown byte-size unit system.
• Unit token '{unit.Symbol}' does not belong to the selected b
• A byte-size format can contain only one distinct unit token.
• Value is not in the correct format
• EiB is outside the range supported by ByteSize.Bits.

AI-assisted analysis of Humanizr/Humanizer@ffc2b77c0f (2026-08-13). Data as JSON: /api/errors/e93171b7ceb78570. Report an issue: GitHub.