diff --git a/thirdpart/build_ffmpeg.js b/thirdpart/build_ffmpeg.js
index c54318a..3860cfc 100644
--- a/thirdpart/build_ffmpeg.js
+++ b/thirdpart/build_ffmpeg.js
@@ -44,7 +44,7 @@ function build() {
 	//make
 	if (0 != spawnSync("make", [
 		"-j", os.cpus().length.toString(),
-	], { stdio: "inherit" }).status) throw new Error("Failed to build ffmpeg");
+	], { stdio: "inherit", cwd: FFMPEG_SOURCE_DIR }).status) throw new Error("Failed to build ffmpeg");
 	//install
 	if (0 != spawnSync("make", [
 		"install",