diff --git a/src/services/process-service.ts b/src/services/process-service.ts
index c6393ecd..ce243b0c 100644
--- a/src/services/process-service.ts
+++ b/src/services/process-service.ts
@@ -49,6 +49,6 @@ export default class ProcessService {
   }
 
   private writePidFile(pid: number) {
-    fs.writeFileSync(ProcessService.PID_PATH, pid)
+    fs.writeFileSync(ProcessService.PID_PATH, pid.toString())
   }
 }