diff --git a/docs/8.0/ayanova/docs/changelog.md b/docs/8.0/ayanova/docs/changelog.md
index 24a632b4..213126cd 100644
--- a/docs/8.0/ayanova/docs/changelog.md
+++ b/docs/8.0/ayanova/docs/changelog.md
@@ -20,6 +20,7 @@ IN PROGRESS
 - Server: in some cases opening a record that has since been deleted (for example from an old link) gave a server error, and a report printed for records of which some had since been deleted failed; it now shows a "not found" message, and the report prints the remaining records.
 - Server: in some cases deleting a record that is still in use elsewhere (for example a customer, unit, part or rate used on a work order, quote or PM) gave a server error; it now always says which kind of record is using it.
 - Server: the server log now records the next automatic backup time (or that automatic backup is off) each time the server starts.
+- Backup: the [number of backups to keep](ops-form-backup.md#number-of-backups-to-keep) can no longer be set below 1; a setting of 0 already kept the most recent backup, the same as 1.
 
 ### AyaNova 8.3.0
 
diff --git a/docs/8.0/ayanova/docs/ops-form-backup.md b/docs/8.0/ayanova/docs/ops-form-backup.md
index 16f39890..3061bf52 100644
--- a/docs/8.0/ayanova/docs/ops-form-backup.md
+++ b/docs/8.0/ayanova/docs/ops-form-backup.md
@@ -158,7 +158,7 @@ Checking this box will cause AyaNova to also back up the attached files in addit
 
 _AyaNova Subscription service keeps one backup by default and this option is not available_
 
-The backup system will automatically remove old backups depending upon this setting. If it is set to 3 then the most recent three backups are kept.
+The backup system will automatically remove old backups depending upon this setting. If it is set to 3 then the most recent three backups are kept. The minimum is 1: the most recent backup is always kept.
 
 If you are following the disaster recovery best practice policy of 10 backup rotation as [suggested above](#10-backup-rotation) then you would only need to keep 1 current backup set.
 
diff --git a/server/AyaNova/Controllers/GlobalOpsBackupSettingsController.cs b/server/AyaNova/Controllers/GlobalOpsBackupSettingsController.cs
index 72de8005..5c117508 100644
--- a/server/AyaNova/Controllers/GlobalOpsBackupSettingsController.cs
+++ b/server/AyaNova/Controllers/GlobalOpsBackupSettingsController.cs
@@ -79,9 +79,15 @@ namespace AyaNova.Api.Controllers
             GlobalOpsBackupSettingsBiz biz = GlobalOpsBackupSettingsBiz.GetBiz(ct, HttpContext);
             if (!Authorized.HasModifyRole(HttpContext.Items, biz.BizType))
                 return StatusCode(403, new ApiNotAuthorizedResponse());
-            var o = await biz.PutAsync(updatedObject); 
+            var o = await biz.PutAsync(updatedObject);
             if (o == null)
-                return StatusCode(409, new ApiErrorResponse(biz.Errors));
+            {
+                //case 4763: the settings can now fail validation, which is not a concurrency conflict
+                if (biz.Errors.Exists(z => z.Code == ApiErrorCode.CONCURRENCY_CONFLICT))
+                    return StatusCode(409, new ApiErrorResponse(biz.Errors));
+                else
+                    return BadRequest(new ApiErrorResponse(biz.Errors));
+            }
             return Ok(ApiOkResponse.Response(new { Concurrency = o.Concurrency }));
         }
 
diff --git a/server/AyaNova/biz/GlobalOpsBackupSettingsBiz.cs b/server/AyaNova/biz/GlobalOpsBackupSettingsBiz.cs
index 90b52200..499299c1 100644
--- a/server/AyaNova/biz/GlobalOpsBackupSettingsBiz.cs
+++ b/server/AyaNova/biz/GlobalOpsBackupSettingsBiz.cs
@@ -112,8 +112,12 @@ namespace AyaNova.Biz
         //Can save or update?
         private void Validate(GlobalOpsBackupSettings inObj)
         {
-
-            //currently nothing to validate
+#if (!SUBSCRIPTION_BUILD)
+            //case 4763: at least the newest backup is always kept, so fewer than 1 is not a setting (it was treated as 1)
+            //the subscription build always keeps 1 and its form doesn't show this setting
+            if (inObj.BackupSetsToKeep < 1)
+                AddError(ApiErrorCode.VALIDATION_INVALID_VALUE, "BackupSetsToKeep");
+#endif
         }