diff --git a/.vscode/extensions/vscode-selfhost-test-provider/src/testOutputScanner.ts b/.vscode/extensions/vscode-selfhost-test-provider/src/testOutputScanner.ts
index dbf0f64ea71..39da7213325 100644
--- a/.vscode/extensions/vscode-selfhost-test-provider/src/testOutputScanner.ts
+++ b/.vscode/extensions/vscode-selfhost-test-provider/src/testOutputScanner.ts
@@ -111,12 +111,14 @@ export class TestOutputScanner implements vscode.Disposable {
 		}
 	}
 
-	protected readonly processData = (data: string) => {
+	protected readonly processData = (data: string | Buffer) => {
 		if (this.args) {
 			this.outputEventEmitter.fire(`./scripts/test ${this.args.join(' ')}`);
 			this.args = undefined;
 		}
 
+		data = data.toString();
+
 		try {
 			const parsed = JSON.parse(data.trim()) as unknown;
 			if (parsed instanceof Array && parsed.length === 2 && typeof parsed[0] === 'string') {