diff --git a/index.js b/index.js
index 8f41848..2107b8b 100644
--- a/index.js
+++ b/index.js
@@ -19,16 +19,16 @@ function msToSrt(timeInMs) {
   }:${seconds < 10 ? "0" + seconds : seconds},${ms}`;
 }
 
-var draftFileName = "draft_content.json";
-let os = process.env.os;
+var draftFileName = "draft_info.json";
+let os = process.platform.toLowerCase();
 switch (os) {
-  case "Windows_NT":
+  case "windows_nt":
     draftFileName = "draft_content.json";
     break;
-  case "Darwin":
+  case "darwin":
     draftFileName = "draft_info.json";
     break;
-  case "Linux":
+  case "linux":
     draftFileName = "draft_info.json";
 }
 console.log("file: " + draftFileName);