diff --git a/PIL/__init__.py b/PIL/__init__.py
index 36c193cfc..7a32533d9 100644
--- a/PIL/__init__.py
+++ b/PIL/__init__.py
@@ -12,7 +12,7 @@
 # ;-)
 
 VERSION = '1.1.7'  # PIL version
-PILLOW_VERSION = '4.0.0'  # Pillow
+PILLOW_VERSION = '4.1.0.dev0'  # Pillow
 
 __version__ = PILLOW_VERSION
 
diff --git a/_imaging.c b/_imaging.c
index c852f6d43..aa2e04778 100644
--- a/_imaging.c
+++ b/_imaging.c
@@ -71,7 +71,7 @@
  * See the README file for information on usage and redistribution.
  */
 
-#define PILLOW_VERSION "4.0.0"
+#define PILLOW_VERSION "4.1.0.dev0"
 
 #include "Python.h"
 
diff --git a/appveyor.yml b/appveyor.yml
index e03afa4c0..deb6d3b1a 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,4 +1,4 @@
-version: 4.0.0.{build}
+version: 4.1.pre.{build}
 clone_folder: c:\pillow
 init:
 - ECHO %PYTHON%
diff --git a/setup.py b/setup.py
index 825d059b8..b0209a399 100755
--- a/setup.py
+++ b/setup.py
@@ -106,7 +106,7 @@ except (ImportError, OSError):
     _tkinter = None
 
 NAME = 'Pillow'
-PILLOW_VERSION = '4.0.0'
+PILLOW_VERSION = '4.1.0.dev0'
 JPEG_ROOT = None
 JPEG2K_ROOT = None
 ZLIB_ROOT = None