diff --git a/internal/captcha/db.go b/internal/captcha/db.go
index 7342cbf..89aecce 100644
--- a/internal/captcha/db.go
+++ b/internal/captcha/db.go
@@ -36,8 +36,7 @@ func (cdb *CaptchaDB) SetExpiration(expire time.Duration) {
 
 	go func() {
 		for {
-			n := time.Now().Second()
-			sleepFor := expiredScanInterval - (time.Duration(n) * time.Second % expiredScanInterval)
+			sleepFor := expiredScanInterval - (time.Duration(time.Now().Second()) % expiredScanInterval)
 			time.Sleep(sleepFor)
 
 			for id, captcha := range cdb.DB {