diff --git a/lib/spack/spack/database.py b/lib/spack/spack/database.py
index 5110e66c7a0..0ada7faa4cb 100644
--- a/lib/spack/spack/database.py
+++ b/lib/spack/spack/database.py
@@ -50,7 +50,9 @@
 _db_dirname = '.spack-db'
 
 # DB version.  This is stuck in the DB file to track changes in format.
-_db_version = Version('0.9.3')
+# Increment by one when the database format changes.
+# versions before 5 were not integers
+_db_version = Version('5')
 
 # Timeout for spack database locks in seconds
 _db_lock_timeout = 120