diff --git a/routes/captcha.ts b/routes/captcha.ts
index c5fc7a499ba..c1a194b6a7c 100644
--- a/routes/captcha.ts
+++ b/routes/captcha.ts
@@ -34,7 +34,7 @@ function captchas () {
 }
 
 captchas.verifyCaptcha = () => (req: Request, res: Response, next: NextFunction) => {
-  CaptchaModel.findOne({ where: { captchaId: req.body.captchaId } }).then((captcha: Captcha | null) => {
+  CaptchaModel.findOne({ where: { captchaId: Number(req.body.captchaId) } }).then((captcha: Captcha | null) => {
     if ((captcha != null) && req.body.captcha === captcha.answer) {
       next()
     } else {