diff --git a/b2share/modules/schemas/validate.py b/b2share/modules/schemas/validate.py
index 5cde8499f9..000dda1b66 100644
--- a/b2share/modules/schemas/validate.py
+++ b/b2share/modules/schemas/validate.py
@@ -54,6 +54,7 @@
                     # the properties which are defined must have this structure
                     "title": {"type": "string"},
                     "description": {"type": "string"},
+                    "unit": {"type": "string"},
                     "type": {
                         "enum": ["boolean", "integer", "number", "string", "array"]
                     },