diff --git a/tests/desktop-logger.test.ts b/tests/desktop-logger.test.ts
index 896bbce..8273020 100644
--- a/tests/desktop-logger.test.ts
+++ b/tests/desktop-logger.test.ts
@@ -52,9 +52,11 @@ describe("bounded desktop logs", () => {
 		const dir = directory(t);
 		for (const name of ["main.log", "main.log.1"]) {
 			const file = path.join(dir, name);
-			// Sparse legacy file: reproduces a huge prior log without allocating it.
+			// Unix creates a sparse hole automatically. Windows can allocate the
+			// entire gap, so keep that fixture small while still exceeding the cap.
+			const legacySize = process.platform === "win32" ? MAX_LOG_BYTES * 3 : 200 * 1024 ** 3;
 			const fd = fs.openSync(file, "w");
-			fs.writeSync(fd, Buffer.from(`recent ${name}\n`), 0, Buffer.byteLength(`recent ${name}\n`), 200 * 1024 ** 3);
+			fs.writeSync(fd, Buffer.from(`recent ${name}\n`), 0, Buffer.byteLength(`recent ${name}\n`), legacySize);
 			fs.closeSync(fd);
 		}
 		let largestRead = 0;