C# Extension static class fails when reading Properties with TryGetValue

Question

I have the below Extension (not mine, borrowed for my implementation, but altered a bit) and I am wondering why is the TryGetValue below failing, despite the fact the the pair (string, object - well, var in my case) seem correct.

public static class somExt
{
    private static string TimeoutPropertyKey = "RequestTimeout";

    public static void SetTimeout( this HttpRequestMessage request, TimeSpan? timeout)
    {
        if (request == null)
            throw new ArgumentNullException(nameof(request));

        request.Properties[TimeoutPropertyKey] = timeout;
    }

    public static TimeSpan? GetTimeout(this HttpRequestMessage request)
    {
        if (request == null)
            throw new ArgumentNullException(nameof(request));

        if (request.Properties.TryGetValue(
                TimeoutPropertyKey, out var value)  // error CS1003: Syntax error, ',' expected - why??
            && value is TimeSpan timeout)
            return timeout;
        return null;
    }
}

Anyone could help me understand and correct the error? Thank you