diff --git a/fmm/__version__.py b/fmm/__version__.py
index f9a2374..ab346cb 100644
--- a/fmm/__version__.py
+++ b/fmm/__version__.py
@@ -3,5 +3,5 @@
 """
 
 __title__ = 'fmm'
-__version__ = '3.0.3'
+__version__ = '4.0.0'
 __description__ = 'An adaptive, kernel-independent, particle FMM implementation Python'