diff --git a/CHANGES.rst b/CHANGES.rst
index be8a2f3..c036b43 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -4,8 +4,14 @@ Changelog
 0.5.x
 ~~~~~
 
-Version0.5.1
-------------
+UNRELEASED
+----------
+
+- Fix an issue where loading a thrift file in a sub-thread will cause an error with ``load_fp``.
+
+
+Version 0.5.1
+-------------
 
 Released on Jun 24, 2024.
 
diff --git a/thriftpy2/__init__.py b/thriftpy2/__init__.py
index 7263ff6..0064e91 100644
--- a/thriftpy2/__init__.py
+++ b/thriftpy2/__init__.py
@@ -5,7 +5,7 @@
 from .hook import install_import_hook, remove_import_hook
 from .parser import load, load_module, load_fp
 
-__version__ = '0.5.1'
+__version__ = '0.5.2b1'
 __python__ = sys.version_info
 __all__ = ["install_import_hook", "remove_import_hook", "load", "load_module",
            "load_fp"]