# Bug Report <!-- Please fill in each section completely. Thank you! --> ### 馃攷 Search Terms - lastIndexOf ### 馃晽 Version & Regression Information - This is a crash in tsserver.js - This happens in 4.2.2, 4.2.3 and next (4.3.0-dev.20210305), but not version 4.1.5 - node version v14.15.4 - windows version 20H2 ### 馃捇 Steps to reproduce This happens consistently for me in the OmniSharp/omnisharp-vscode repository, when opening a typescript file with 4.2 installed. 1. git clone https://github.com/OmniSharp/omnisharp-vscode.git 2. cd omnisharp-vscode 3. npm install 4. npm install -g typescript@4.2.2 5. code . 6. Configure vscode to use the global ts server (for me this is `"typescript.tsdk": "C:\\Users\\phil\\AppData\\Roaming\\npm\\node_modules\\typescript\\lib",`) 7. Restart code 8. Open the TypeScript output to view errors ### 馃檨 Actual behavior The TypeScript language server crashes. Attached is a sample log: [tsserver.zip](https://github.com/microsoft/TypeScript/files/6093180/tsserver.zip) ### 馃檪 Expected behavior It to not crash. ### Related Issues There's a couple of related issues in vscode repo such as microsoft/vscode#115905