diff --git a/src/index.ts b/src/index.ts
index d2c67c1..b73f3db 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -64,8 +64,8 @@ program
   .description(`
     List all URLs in sitemap.
   `)
-  .option('--probability', 'the chance the line will pass', '10')
-  .action(() => {
+  .option('--probability <probability>', 'the chance the line will pass', (value) => parseInt(value))
+  .action((options) => {
     const rl = readline.createInterface({
       input: process.stdin,
       output: process.stdout,
@@ -75,7 +75,7 @@ program
     rl.on('line', (line) => {
       try {
         new URL(line);
-        if (Math.random() <= 0.1) {
+        if (Math.random() <= (options.probability / 100)) {
           console.log(line);
         }
       } catch {