https://github.com/dotnet/runtime/blame/a566fd59fc34d3f73da1b8eeaab613ab0c1fc9b5/src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/Http2Stream.cs#L1127-L1127

With a recent repro from an internal customer, I'm hitting assert at this line as I'm testing with Debug build. I can share repro privately.