diff --git a/HISTORY.rst b/HISTORY.rst
index fa81cec0..4127fdca 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -8,6 +8,9 @@ PlatformIO Core 5
 
 **A professional collaborative platform for embedded development**
 
+5.2.1 (2021-??-??)
+~~~~~~~~~~~~~~~~~~
+
 5.2.0 (2021-09-13)
 ~~~~~~~~~~~~~~~~~~
 
diff --git a/docs b/docs
index c9d2ef9a..395b056f 160000
--- a/docs
+++ b/docs
@@ -1 +1 @@
-Subproject commit c9d2ef9abe4d349465609616fc5c2b69b4a0823d
+Subproject commit 395b056f8e6ee5cbb7e622465622e7b08431868f
diff --git a/platformio/__init__.py b/platformio/__init__.py
index 0314286b..dcb27382 100644
--- a/platformio/__init__.py
+++ b/platformio/__init__.py
@@ -14,7 +14,7 @@
 
 import sys
 
-VERSION = (5, 2, 0)
+VERSION = (5, 2, "1a1")
 __version__ = ".".join([str(s) for s in VERSION])
 
 __title__ = "platformio"