diff --git a/msprime/__init__.py b/msprime/__init__.py
index ea1551dce..ebcc0e5c2 100644
--- a/msprime/__init__.py
+++ b/msprime/__init__.py
@@ -28,4 +28,4 @@
 
 from msprime.trees import *  # NOQA
 
-__version__ = '0.1.2.dev1'
+__version__ = '0.1.2.a1'