diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index c1a271bb0af..2579518fe17 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -1675,7 +1675,7 @@ declare namespace ts {
     export type FlowNode = AfterFinallyFlow | PreFinallyFlow | FlowStart | FlowLabel | FlowAssignment | FlowCall | FlowCondition | FlowSwitchClause | FlowArrayMutation;
     export interface FlowNodeBase {
         flags: FlowFlags;
-        id: number | undefined;
+        id?: number;
     }
     export interface FlowLock {
         locked?: boolean;
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
index 0bb7d724ee0..4417b52af36 100644
--- a/tests/baselines/reference/api/typescript.d.ts
+++ b/tests/baselines/reference/api/typescript.d.ts
@@ -1675,7 +1675,7 @@ declare namespace ts {
     export type FlowNode = AfterFinallyFlow | PreFinallyFlow | FlowStart | FlowLabel | FlowAssignment | FlowCall | FlowCondition | FlowSwitchClause | FlowArrayMutation;
     export interface FlowNodeBase {
         flags: FlowFlags;
-        id: number | undefined;
+        id?: number;
     }
     export interface FlowLock {
         locked?: boolean;