diff --git a/lib/spack/spack/__init__.py b/lib/spack/spack/__init__.py
index 4486221a18c..06ba69a803e 100644
--- a/lib/spack/spack/__init__.py
+++ b/lib/spack/spack/__init__.py
@@ -4,7 +4,7 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 #: PEP440 canonical <major>.<minor>.<micro>.<devN> string
-__version__ = "0.19.0.dev0"
+__version__ = "0.20.0.dev0"
 spack_version = __version__