diff --git a/.bumpversion.cfg b/.bumpversion.cfg
index 43c6d06..a91953e 100644
--- a/.bumpversion.cfg
+++ b/.bumpversion.cfg
@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 0.3.1
+current_version = 0.4.0
 tag = False
 commit = False
 parse = ^
diff --git a/rxnmapper/__init__.py b/rxnmapper/__init__.py
index 090e7a0..2c0e5fa 100644
--- a/rxnmapper/__init__.py
+++ b/rxnmapper/__init__.py
@@ -1,7 +1,7 @@
 """rxnmapper initialization."""
 
 __name__ = "rxnmapper"
-__version__ = "0.3.1"  # managed by bump2version
+__version__ = "0.4.0"  # managed by bump2version
 
 
 from .batched_mapper import BatchedMapper