diff --git a/backend/src/products/products.service.ts b/backend/src/products/products.service.ts
index 3dd3244e..474f7765 100644
--- a/backend/src/products/products.service.ts
+++ b/backend/src/products/products.service.ts
@@ -136,11 +136,11 @@ export class ProductsService {
     }
 
     if (typeof data.canonicalName === 'string') {
-      updateData.canonicalName = data.canonicalName.trim() || null;
+      updateData.canonicalName = data.canonicalName.trim() || undefined;
     }
 
     if (typeof data.category === 'string') {
-      updateData.category = data.category.trim() || null;
+      updateData.category = data.category.trim() || undefined;
     }
 
     return this.prisma.product.update({