diff --git a/VERSION b/VERSION
index 8ff5d387..1d0ba9ea 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.5.0.dev
+0.4.0
diff --git a/setup.cfg b/setup.cfg
index 02384518..a05259f6 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -8,7 +8,7 @@ keywords = quantum, physics, dynamics
 license = BSD 3-Clause License
 license_files = LICENSE
 classifiers =
-    Development Status :: 2 - Pre-Alpha
+    Development Status :: 5 - Production/Stable
     Intended Audience :: Science/Research
     License :: OSI Approved :: BSD License
     Programming Language :: Python