# Stack traces are missing source information for frames with debug information in the Portable PDB format when running on .NET Framework 4.7.1
## Symptoms
An application that formats stack traces is missing source information for some or all frames. This includes stack traces formatted via [System.Exception.ToString()](https://docs.microsoft.com/en-us/dotnet/api/system.exception.tostring?view=netframework-4.7.1), [System.Exception.StackTrace](https://docs.microsoft.com/en-us/dotnet/api/system.exception.stacktrace?view=netframework-4.7.1) and [System.Diagnostics.StackTrace.ToString()](https://docs.microsoft.com/en-us/dotnet/api/system.diagnostics.stacktrace.tostring?view=netframework-4.7.1).
The frames missing source information reside in assemblies that have pdbs in the [Portable PDB format](https://github.com/dotnet/core/blob/master/Documentation/diagnostics/portable_pdb.md) present on disk.
## Cause
The .NET Framework 4.7.1 added support for detecting and parsing the Portable PDB file format to show file and line number information in stack traces. However, due to an [implementation issue](https://github.com/Microsoft/dotnet/blob/master/releases/net471/KnownIssues/517815-BCL%20Applications%20making%20heavy%20use%20of%20System.Diagnostics.StackTrace%20might%20run%20more%20slowly%20on%20.NET%204.7.1.md), the feature had an unacceptable performance impact and Microsoft intentionally disabled it.
## Workarounds
- If you control the build process for the problematic assemblies you may be able to configure it to generate the classic Windows PDB format instead.
- You can use the [PDB conversion tool](https://github.com/dotnet/symreader-converter) to convert the Portable PDBs into the classic Windows PDB format and deploy those with the application instead.
