diff --git a/app/database/crud/promo_group.py b/app/database/crud/promo_group.py
index 0da9712c..39a97dc0 100644
--- a/app/database/crud/promo_group.py
+++ b/app/database/crud/promo_group.py
@@ -166,7 +166,7 @@ async def update_promo_group(
         group.device_discount_percent = max(0, min(100, device_discount_percent))
     if period_discounts is not None:
         normalized_period_discounts = _normalize_period_discounts(period_discounts)
-        group.period_discounts = normalized_period_discounts or None
+        group.period_discounts = normalized_period_discounts if normalized_period_discounts else None
     if auto_assign_total_spent_kopeks is not None:
         value = max(0, auto_assign_total_spent_kopeks)
         group.auto_assign_total_spent_kopeks = value if value > 0 else None
diff --git a/app/webapi/schemas/promo_groups.py b/app/webapi/schemas/promo_groups.py
index ccd55242..0c2a0109 100644
--- a/app/webapi/schemas/promo_groups.py
+++ b/app/webapi/schemas/promo_groups.py
@@ -18,7 +18,9 @@ def _normalize_period_discounts(value: dict[object, object] | None) -> dict[int,
             except (TypeError, ValueError):
                 continue
 
-    return normalized or None
+    # Return empty dict (not None) so the backend can distinguish
+    # "clear all discounts" ({}) from "don't touch discounts" (None/absent).
+    return normalized
 
 
 class PromoGroupResponse(BaseModel):