diff --git a/src/edr_pydantic/unit.py b/src/edr_pydantic/unit.py
index 08110a2..d9d1489 100644
--- a/src/edr_pydantic/unit.py
+++ b/src/edr_pydantic/unit.py
@@ -9,6 +9,8 @@
 class Symbol(EdrBaseModel, extra="allow"):
     value: str
     type: str
+    title: Optional[str] = None
+    description: Optional[str] = None
 
 
 class Unit(EdrBaseModel):