diff --git a/erpnext/manufacturing/doctype/sub_operation/sub_operation.json b/erpnext/manufacturing/doctype/sub_operation/sub_operation.json
index c7530e41aca..36160fec699 100644
--- a/erpnext/manufacturing/doctype/sub_operation/sub_operation.json
+++ b/erpnext/manufacturing/doctype/sub_operation/sub_operation.json
@@ -16,7 +16,8 @@
    "fieldtype": "Link",
    "in_list_view": 1,
    "label": "Operation",
-   "options": "Operation"
+   "options": "Operation",
+   "reqd": 1
   },
   {
    "default": "0",
@@ -40,7 +41,7 @@
  "index_web_pages_for_search": 1,
  "istable": 1,
  "links": [],
- "modified": "2025-08-04 16:15:11.425349",
+ "modified": "2026-04-13 12:17:33.776504",
  "modified_by": "Administrator",
  "module": "Manufacturing",
  "name": "Sub Operation",
diff --git a/erpnext/manufacturing/doctype/sub_operation/sub_operation.py b/erpnext/manufacturing/doctype/sub_operation/sub_operation.py
index f4bb62e8f6c..a34a96fc1a5 100644
--- a/erpnext/manufacturing/doctype/sub_operation/sub_operation.py
+++ b/erpnext/manufacturing/doctype/sub_operation/sub_operation.py
@@ -16,7 +16,7 @@ class SubOperation(Document):
 		from frappe.types import DF
 
 		description: DF.SmallText | None
-		operation: DF.Link | None
+		operation: DF.Link
 		parent: DF.Data
 		parentfield: DF.Data
 		parenttype: DF.Data