Updated the changelog
diff --git a/CHANGES.rst b/CHANGES.rst
index b5089cc..63a7d3b 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,10 @@
+UNRELEASED
+==========
+
+- Backported bpo-21423: Add an initializer argument to {Process,Thread}PoolExecutor
+  (only ThreadPoolExecutor for now; PR by Fahrzin Hemmati)
+
+
 3.3.0
 =====