diff --git a/DCHdigi/dataFormatExtension/driftChamberHit.yaml b/DCHdigi/dataFormatExtension/driftChamberHit.yaml
index 7afd9b2..aef3175 100644
--- a/DCHdigi/dataFormatExtension/driftChamberHit.yaml
+++ b/DCHdigi/dataFormatExtension/driftChamberHit.yaml
@@ -1,4 +1,5 @@
 ---
+schema_version: 1
 options:
   # should getters / setters be prefixed with get / set?
   getSyntax: True