diff --git a/pyproject.toml b/pyproject.toml
index 21c657c..0d9aca2 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "labelmerge"
-version = "0.3.0"
+version = "0.4.0-pre.1"
 description = "Snakebids app for merging multiple label maps."
 authors = [
     "Jason Kai <tkai@uwo.ca>",