diff --git a/README.md b/README.md
index af385f3..993ed4a 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,7 @@ Atomically and asynchronously writes data to a file, replacing the file if it al
 exists.  data can be a string or a buffer.
 
 The file is initially named `filename + "." + murmurhex(__filename, process.pid, ++invocations)`.
+Note that `require('worker_threads').threadId` is used in addition to `process.pid` if running inside of a worker thread.
 If writeFile completes successfully then, if passed the **chown** option it will change
 the ownership of the file. Finally it renames the file back to the filename you specified. If
 it encounters errors at any of these steps it will attempt to unlink the temporary file and then
diff --git a/index.js b/index.js
index 3b5607d..cdaeac0 100644
--- a/index.js
+++ b/index.js
@@ -10,11 +10,26 @@ var onExit = require('signal-exit')
 var path = require('path')
 var activeFiles = {}
 
+// if we run inside of a worker_thread, `process.pid` is not unique
+/* istanbul ignore next */
+var threadId = (function getId () {
+  try {
+    var workerThreads = require('worker_threads')
+
+    /// if we are in main thread, this is set to `0`
+    return workerThreads.threadId
+  } catch (e) {
+    // worker_threads are not available, fallback to 0
+    return 0
+  }
+})()
+
 var invocations = 0
 function getTmpname (filename) {
   return filename + '.' +
     MurmurHash3(__filename)
       .hash(String(process.pid))
+      .hash(String(threadId))
       .hash(String(++invocations))
       .result()
 }