diff --git a/src/system/game-data.ts b/src/system/game-data.ts
index d64aa8f8e91..40f24fc8326 100644
--- a/src/system/game-data.ts
+++ b/src/system/game-data.ts
@@ -1709,7 +1709,7 @@ export class GameData {
   }
 
   getFormAttr(formIndex: integer): bigint {
-    return BigInt(1 << (7 + formIndex));
+    return BigInt(1) << BigInt(7 + formIndex);
   }
 
   consolidateDexData(dexData: DexData): void {