diff --git a/lib/xos-config/xosconfig/default.py b/lib/xos-config/xosconfig/default.py
index 2e37229..4f6ec23 100644
--- a/lib/xos-config/xosconfig/default.py
+++ b/lib/xos-config/xosconfig/default.py
@@ -14,7 +14,10 @@
 
 DEFAULT_VALUES = {
     "xos_dir": "/opt/xos",
-    "desired_state": "load", # synchronizers - default to "load"
+    "desired_state": "load",  # synchronizers - default to "load"
+    # by default version in not set,
+    # we can't make it mandatory as we're reading multiple files in the synchronizers
+    "core_version": None,
     # The configuration below inherits from the standard config of the Python logging module
     # See: https://docs.python.org/2/library/logging.config.html
     # multistructlog supports this config in all of its generality
diff --git a/lib/xos-config/xosconfig/synchronizer-config-schema.yaml b/lib/xos-config/xosconfig/synchronizer-config-schema.yaml
index 357e8d9..cba845f 100644
--- a/lib/xos-config/xosconfig/synchronizer-config-schema.yaml
+++ b/lib/xos-config/xosconfig/synchronizer-config-schema.yaml
@@ -15,6 +15,8 @@
 map:
   name:
     type: str
+  core_version:
+    type: str
   desired_state:
     type: str
   xos_dir: