diff --git a/db_schema b/db_schema
index 9e6ca04..3134bcf 100644
--- a/db_schema
+++ b/db_schema
@@ -30,7 +30,7 @@ Enum part_type {
 Table parts {
   id int [pk]
   product_id int [ref: > products.id, not null]
-  type part_type_type [not null]
+  type part_type [not null]
   color_top int [ref: > colors.id, not null]
   color_back int [ref: > colors.id, not null]
   finish_top finish_type [not null]
@@ -112,6 +112,11 @@ Table events {
   indexes {
     (part_id, ordinal) [unique]
   }
+
+  checks {
+    `type != 'OPERATION' OR operation_id IS NOT NULL` [name: 'chk_event_operation_required']
+    `type = 'OPERATION' OR operation_id IS NULL` [name: 'chk_event_operation_forbidden']
+  }
 }
 
 Table production_lists {