diff --git a/modules/gacha/rand.go b/modules/gacha/rand.go
index 6ffa2b0..2e82055 100644
--- a/modules/gacha/rand.go
+++ b/modules/gacha/rand.go
@@ -16,7 +16,7 @@ func (cryptoSource) Int63() int64 {
 	if err != nil {
 		panic(err)
 	}
-	return int64(value ^ uint64(1<<63))
+	return int64(value & ^uint64(1<<63))
 }
 
 func (cryptoSource) Seed(seed int64) {}