diff --git a/erpnext/patches.txt b/erpnext/patches.txt
index 72db8ad063..f357b3d968 100644
--- a/erpnext/patches.txt
+++ b/erpnext/patches.txt
@@ -615,3 +615,4 @@ erpnext.patches.v11_1.set_missing_opportunity_from
 erpnext.patches.v12_0.set_quotation_status
 erpnext.patches.v12_0.set_priority_for_support
 erpnext.patches.v12_0.delete_priority_property_setter
+erpnext.patches.v12_0.set_default_batch_size
diff --git a/erpnext/patches/v12_0/set_default_batch_size.py b/erpnext/patches/v12_0/set_default_batch_size.py
new file mode 100644
index 0000000000..76a355bcf2
--- /dev/null
+++ b/erpnext/patches/v12_0/set_default_batch_size.py
@@ -0,0 +1,20 @@
+import frappe
+
+
+def execute():
+    frappe.reload_doc("manufacturing", "doctype", "bom_operation")
+    frappe.reload_doc("manufacturing", "doctype", "work_order_operation")
+
+    frappe.db.sql("""
+        UPDATE
+            `tabBOM Operation` bo
+        SET
+            bo.batch_size = 1
+    """)
+    frappe.db.sql("""
+        UPDATE
+            `tabWork Order Operation` wop
+        SET
+            wop.batch_size = 1
+    """)
+    frappe.db.commit()