diff --git a/src/middlewares/existance.js b/src/middlewares/existance.js
index 73c2c88..a796b98 100644
--- a/src/middlewares/existance.js
+++ b/src/middlewares/existance.js
@@ -3,7 +3,9 @@ import responseCodes from '../response/responseCodes.js';
 import GroupService from '../services/group.js';
 
 const groupExists = async (req, res, next) => {
-    let groupId = req.params.groupId || req.body.groupId;
+    let groupId = Number(req.params.groupId || req.body.groupId);
+
+    if (isNaN(groupId)) throw new customError(`groupId is not a number`, responseCodes.responses.groups.id_not_found)
 
     let group = await GroupService.getById(groupId);