diff --git a/ocpi/modules/commands/v_2_1_1/schemas.py b/ocpi/modules/commands/v_2_1_1/schemas.py
index b3a3f1a..a848812 100644
--- a/ocpi/modules/commands/v_2_1_1/schemas.py
+++ b/ocpi/modules/commands/v_2_1_1/schemas.py
@@ -23,7 +23,7 @@ class ReserveNow(BaseModel):
     expiry_date: DateTime
     reservation_id: int
     location_id: String(36)  # type: ignore
-    evse_uid: String(39) | None  # type: ignore
+    evse_uid: String(39) | None = None  # type: ignore
 
 
 class StartSession(BaseModel):
@@ -34,7 +34,7 @@ class StartSession(BaseModel):
     response_url: URL
     token: Token
     location_id: String(39)  # type: ignore
-    evse_uid: String(39) | None  # type: ignore
+    evse_uid: String(39) | None = None  # type: ignore
 
 
 class StopSession(BaseModel):
diff --git a/ocpi/modules/commands/v_2_2_1/schemas.py b/ocpi/modules/commands/v_2_2_1/schemas.py
index 2ad17de..798a692 100644
--- a/ocpi/modules/commands/v_2_2_1/schemas.py
+++ b/ocpi/modules/commands/v_2_2_1/schemas.py
@@ -46,8 +46,8 @@ class ReserveNow(BaseModel):
     expiry_date: DateTime
     reservation_id: CiString(36)  # type: ignore
     location_id: CiString(36)  # type: ignore
-    evse_uid: CiString(36) | None  # type: ignore
-    authorization_reference: CiString(36) | None  # type: ignore
+    evse_uid: CiString(36) | None = None  # type: ignore
+    authorization_reference: CiString(36) | None = None  # type: ignore
 
 
 class StartSession(BaseModel):
@@ -58,9 +58,9 @@ class StartSession(BaseModel):
     response_url: URL
     token: Token
     location_id: CiString(36)  # type: ignore
-    evse_uid: CiString(36) | None  # type: ignore
-    connector_id: CiString(36) | None  # type: ignore
-    authorization_reference: CiString(36) | None  # type: ignore
+    evse_uid: CiString(36) | None = None  # type: ignore
+    connector_id: CiString(36) | None = None  # type: ignore
+    authorization_reference: CiString(36) | None = None  # type: ignore
 
 
 class StopSession(BaseModel):
diff --git a/ocpi/modules/commands/v_2_3_0/schemas.py b/ocpi/modules/commands/v_2_3_0/schemas.py
index 31a6c93..34f3937 100644
--- a/ocpi/modules/commands/v_2_3_0/schemas.py
+++ b/ocpi/modules/commands/v_2_3_0/schemas.py
@@ -46,8 +46,8 @@ class ReserveNow(BaseModel):
     expiry_date: DateTime
     reservation_id: CiString(36)  # type: ignore
     location_id: CiString(36)  # type: ignore
-    evse_uid: CiString(36) | None  # type: ignore
-    authorization_reference: CiString(36) | None  # type: ignore
+    evse_uid: CiString(36) | None = None  # type: ignore
+    authorization_reference: CiString(36) | None = None  # type: ignore
 
 
 class StartSession(BaseModel):
@@ -58,9 +58,9 @@ class StartSession(BaseModel):
     response_url: URL
     token: Token
     location_id: CiString(36)  # type: ignore
-    evse_uid: CiString(36) | None  # type: ignore
-    connector_id: CiString(36) | None  # type: ignore
-    authorization_reference: CiString(36) | None  # type: ignore
+    evse_uid: CiString(36) | None = None  # type: ignore
+    connector_id: CiString(36) | None = None  # type: ignore
+    authorization_reference: CiString(36) | None = None  # type: ignore
 
 
 class StopSession(BaseModel):