diff --git a/scripts/update-unicode-ids.ts b/scripts/update-unicode-ids.ts
index 82fb809..c44cffe 100644
--- a/scripts/update-unicode-ids.ts
+++ b/scripts/update-unicode-ids.ts
@@ -69,11 +69,11 @@ export function isIdContinue(cp: number): boolean {
 }
 
 function isLargeIdStart(cp: number): boolean {
-    return isInRange(cp, largeIdStartRanges || (largeIdStartRanges = initLargeIdStartRanges()))
+    return isInRange(cp, largeIdStartRanges ?? (largeIdStartRanges = initLargeIdStartRanges()))
 }
 
 function isLargeIdContinue(cp: number): boolean {
-    return isInRange(cp, largeIdContinueRanges || (largeIdContinueRanges = initLargeIdContinueRanges()))
+    return isInRange(cp, largeIdContinueRanges ?? (largeIdContinueRanges = initLargeIdContinueRanges()))
 }
 
 function initLargeIdStartRanges(): number[] {
diff --git a/scripts/update-unicode-properties.ts b/scripts/update-unicode-properties.ts
index 08d1088..41c4903 100644
--- a/scripts/update-unicode-properties.ts
+++ b/scripts/update-unicode-properties.ts
@@ -195,7 +195,7 @@ function makeClassDeclarationCode(versions: string[]): string {
     const getters = versions
         .map(
             (v) =>
-                `public get es${v}(): Set<string> { return this._set${v} || (this._set${v} = new Set(this._raw${v}.split(" "))) }`,
+                `public get es${v}(): Set<string> { return this._set${v} ?? (this._set${v} = new Set(this._raw${v}.split(" "))) }`,
         )
         .join("\n")