Why is there a character limit on property values in web.config configuration sections?

Recently, I've encountered an exception that states the following:

Critical Unexpected Error Occured:System.Configuration.ConfigurationErrorsException: The value for the property 'foo' is not valid. The error is: The string must be no more than 999 characters long.

However, I can't find any documentation on such an error, and everything seems to state that there is no character limit on these values.

Naturally, to solve the issue, I can make the string shorter. But this seems interesting that it would have this seemingly arbitrary character limit.

Is there any documentation that would be relevant to this issue to describe why this is happening, and the reasons behind the character limit?

The full stack trace is as follows:

Critical Unexpected Error Occured:System.Configuration.ConfigurationErrorsException: The value for the property 'foo' is not valid. The error is: The string must be no more than 999 characters long. (C:\workspace\foobar\src\Manager\foo\bar.Web\web.config line 34) at System.Configuration.BaseConfigurationRecord.EvaluateOne(String[] keys, SectionInput input, Boolean isTrusted, FactoryRecord factoryRecord, SectionRecord sectionRecord, Object parentResult) at System.Configuration.BaseConfigurationRecord.Evaluate(FactoryRecord factoryRecord, SectionRecord sectionRecord, Object parentResult, Boolean getLkg, Boolean getRuntimeObject, Object& result, Object& resultRuntimeObject) at System.Configuration.BaseConfigurationRecord.GetSectionRecursive(String configKey, Boolean getLkg, Boolean checkPermission, Boolean getRuntimeObject, Boolean requestIsHere, Object& result, Object& resultRuntimeObject) at System.Configuration.BaseConfigurationRecord.GetSection(String configKey) at System.Web.HttpContext.GetSection(String sectionName) at System.Web.Configuration.HttpConfigurationSystem.GetSection(String sectionName) at System.Web.Configuration.HttpConfigurationSystem.System.Configuration.Internal.IInternalConfigSystem.GetSection(String configKey)