diff --git a/pyproject.toml b/pyproject.toml
index a61c403c..b2e6da5c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "burnman"
-version = "2.1.0"
+version = "2.1.1a"
 description = "A thermoelastic and thermodynamic toolkit for the Earth and planetary sciences"
 license = "GPL"
 authors = ["The BurnMan Team <bob.myhill@bristol.ac.uk>",]