diff --git a/src/routes/prediction.ts b/src/routes/prediction.ts
index fc50d04..9fc2bf6 100644
--- a/src/routes/prediction.ts
+++ b/src/routes/prediction.ts
@@ -17,9 +17,10 @@ router.post('/prediction/new', (req, res, next) => {
 });
 
 router.post('/prediction/compare', async (req, res, next) => {
-	const valA = (await PredictionModel.findOne({ name: req.body.nameA })).value;
-	const valB = (await PredictionModel.findOne({ name: req.body.nameB })).value;
-	res.json(valB - valA);
+	const valA = await PredictionModel.findOne({ name: req.body.nameA });
+	const valB = await PredictionModel.findOne({ name: req.body.nameB });
+	if(!valA || !valB) next(new Error("invalid prediction name"));
+	res.json(valB.value - valA.value);
 });