diff --git a/CHANGELOG.md b/CHANGELOG.md
index 36e856b..e4a911f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 
+## [5.1.1] - 2023-04-02
+
+- fixed `Unknown identifier : _pollPeriod`
+
+
 ## [5.1.0] - 2023-04-02
 
 ### Added
diff --git a/haxelib.json b/haxelib.json
index f463093..43abae5 100644
--- a/haxelib.json
+++ b/haxelib.json
@@ -11,6 +11,6 @@
    "description": "A haxelib with cross-platform concurrency functions and classes (thread-pool, task executor/scheduler, re-entrant lock, semaphore, atomic int/bool, thread-safe collections/queues)",
    "contributors": ["vegardit"],
    "releasenote": "See https://github.com/vegardit/haxe-concurrent/blob/main/CHANGELOG.md",
-   "version": "5.1.0",
+   "version": "5.1.1",
    "dependencies": { }
 }
diff --git a/src/hx/concurrent/thread/ThreadPool.hx b/src/hx/concurrent/thread/ThreadPool.hx
index e9eb1f0..21bbbb6 100644
--- a/src/hx/concurrent/thread/ThreadPool.hx
+++ b/src/hx/concurrent/thread/ThreadPool.hx
@@ -111,7 +111,7 @@ class ThreadPool extends ServiceBase {
                if (task == null) {
                   if(state != RUNNING)
                      break;
-                  Sys.sleep(_pollPeriod);
+                  Sys.sleep(pollPeriod);
                } else {
                   try {
                      _workingThreadCount++;