diff --git a/examples/calculator/src/index.tsx b/examples/calculator/src/index.tsx
index 852911990..328248060 100644
--- a/examples/calculator/src/index.tsx
+++ b/examples/calculator/src/index.tsx
@@ -85,7 +85,7 @@ function safeEval(expr: string): string {
     if (tokens.length === 0) return '0';
 
     // Handle initial negative number
-    if (tokens[0] === '-' && tokens.length > 1 && !isNaN(Number(tokens[1]))) {
+    if (tokens[0] === '-' && tokens.length > 1 && !Number.isNaN(Number(tokens[1]))) {
         tokens.splice(0, 2, '-' + tokens[1]);
     }
 
diff --git a/packages/ui/src/prompts.ts b/packages/ui/src/prompts.ts
index b92bb28ba..b248a6ac4 100644
--- a/packages/ui/src/prompts.ts
+++ b/packages/ui/src/prompts.ts
@@ -113,7 +113,7 @@ async function promptSelect<T = string>(options: SelectPromptOptions<T>): Promis
                     return;
                 }
                 const n = parseInt(trimmed, 10);
-                if (!isNaN(n) && n >= 1 && n <= choices.length) {
+                if (!Number.isNaN(n) && n >= 1 && n <= choices.length) {
                     rl.close();
                     resolve(choices[n - 1].value);
                     return;