Invalid Base exception in DateField.StringToTime()

The Lucene.Net.Documents.DateField.StringToTime() method called by StringToDate() appears to specify an invalid value for the base in the .NET Convert.ToInt64() call. When a DateField value in a legacy index is read, or Lucene.NET 2.9.4 is used with legacy code that relies upon DateField, the following exception occurs whenever StringToDate() is called:

System.ArgumentException: Invalid Base.
at System.Convert.ToInt64(String value, Int32 fromBase)
at Lucene.Net.Documents.DateField.StringToTime(String s)
at Lucene.Net.Documents.DateField.StringToDate(String s)