diff --git a/lib/index.js b/lib/index.js
index 6013894..1419ef5 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -30,7 +30,9 @@ function getTmpname (filename) {
   return filename + '.' +
     MurmurHash3(__filename)
       .hash(String(process.pid))
+      .hash('\0')
       .hash(String(threadId))
+      .hash('\0')
       .hash(String(++invocations))
       .result()
 }