diff --git a/buildtools/version.py b/buildtools/version.py
index 38c12610..32977286 100644
--- a/buildtools/version.py
+++ b/buildtools/version.py
@@ -23,10 +23,10 @@ PROJECT_NAME     = 'wxPython'
 # MINOR numbers each time there is a corresponding bump in the wxWidgets
 # version numbers.
 VER_MAJOR        = 4
-VER_MINOR        = 0
+VER_MINOR        = 1
 VER_RELEASE      = 0
 
-VER_FLAGS        = ""     # wxPython release flags
+VER_FLAGS        = "a1"     # wxPython release flags
 
 # The VER_FLAGS value is appended to the version number constructed from the
 # first 3 components and should be set according to the following patterns.
@@ -61,6 +61,6 @@ VER_FLAGS        = ""     # wxPython release flags
 
 # The version numbers of wxWidgets to be used in the build
 wxVER_MAJOR        = 3
-wxVER_MINOR        = 0
+wxVER_MINOR        = 1
 wxVER_RELEASE      = 0  # only used when wxVER_MINOR is an odd value