diff --git a/backend/src/utils/validation.js b/backend/src/utils/validation.js
index 78cd973..09ec75d 100644
--- a/backend/src/utils/validation.js
+++ b/backend/src/utils/validation.js
@@ -93,10 +93,10 @@ const userProductSchema = Joi.object({
     Joi.object({
       id: Joi.number().optional(), // For frontend temporary IDs
       spreaderBrand: Joi.string().max(100).required(),
-      spreaderModel: Joi.string().max(100).allow(null, '').optional(),
+      spreaderModel: Joi.string().max(100).allow(null, '', undefined).optional(),
       settingValue: Joi.string().max(20).required(),
-      rateDescription: Joi.string().max(200).allow(null, '').optional(),
-      notes: Joi.string().allow(null, '').optional()
+      rateDescription: Joi.string().max(200).allow(null, '', undefined).optional(),
+      notes: Joi.string().allow(null, '', undefined).optional()
     })
   ).optional()
 });
diff --git a/frontend/src/pages/Products/Products.js b/frontend/src/pages/Products/Products.js
index 22f86c2..9eb1c64 100644
--- a/frontend/src/pages/Products/Products.js
+++ b/frontend/src/pages/Products/Products.js
@@ -821,10 +821,10 @@ const EditProductModal = ({ product, onSubmit, onCancel, sharedProducts, categor
         ...(formData.productType === 'granular' && editSpreaderSettings.length > 0 && {
           spreaderSettings: editSpreaderSettings.map(setting => ({
             spreaderBrand: setting.spreaderBrand,
-            spreaderModel: setting.spreaderModel && setting.spreaderModel.trim() ? setting.spreaderModel.trim() : null,
+            spreaderModel: setting.spreaderModel && setting.spreaderModel.trim() ? setting.spreaderModel.trim() : '',
             settingValue: setting.settingValue,
-            rateDescription: setting.rateDescription && setting.rateDescription.trim() ? setting.rateDescription.trim() : null,
-            notes: setting.notes && setting.notes.trim() ? setting.notes.trim() : null
+            rateDescription: setting.rateDescription && setting.rateDescription.trim() ? setting.rateDescription.trim() : '',
+            notes: setting.notes && setting.notes.trim() ? setting.notes.trim() : ''
           }))
         })
       };