diff --git a/CHANGELOG.md b/CHANGELOG.md
index 85faf0672..af0976148 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## Version 0.40.0
+
+_In development._
+
 ## Version 0.39.0
 
 ([Full Changelog](https://github.com/unitaryfund/mitiq/compare/v0.38.0...v0.39.0))
diff --git a/VERSION.txt b/VERSION.txt
index 4ef2eb086..1994dd092 100644
--- a/VERSION.txt
+++ b/VERSION.txt
@@ -1 +1 @@
-0.39.0
+0.40.0dev