diff --git a/.bumpversion.cfg b/.bumpversion.cfg
index 087c86f..53ab70c 100644
--- a/.bumpversion.cfg
+++ b/.bumpversion.cfg
@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 0.5.0
+current_version = 0.5.1-dev1
 commit = True
 tag = True
 parse = (?P<major>\d+)\.(?P<minor>\d+)\.(?P<patch>\d+)(\-(?P<release>(rc|dev))(?P<build>\d+))?
diff --git a/pyproject.toml b/pyproject.toml
index 006cc28..06c4d89 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "focus-spec-validator"
-version = "0.5.0"
+version = "0.5.1-dev1"
 description = "FOCUS spec validator."
 authors = []
 readme = "README.md"