diff --git a/apps/as/src/pages/sewer-bsc-plan/ui/previous-plan-lookup-dialog.tsx b/apps/as/src/pages/sewer-bsc-plan/ui/previous-plan-lookup-dialog.tsx
index 843f0251b..162efec34 100644
--- a/apps/as/src/pages/sewer-bsc-plan/ui/previous-plan-lookup-dialog.tsx
+++ b/apps/as/src/pages/sewer-bsc-plan/ui/previous-plan-lookup-dialog.tsx
@@ -33,7 +33,7 @@ interface PreviousPlanLookupDialogProps {
   /** 부모 폼 `sewerBscPlan.sido` 표시명 */
   initialSidoNm?: string;
   /** 부모 폼 `sewerBscPlan.gugun` 표시명 */
-  initialGugunNm?: string;
+  initialGugunNm?: string | null;
 }
 
 const EMPTY_ADST_LIST: CmCdAdstDstrComboResponseDto[] = [];