diff --git a/src/ssn/decryption/decryptChunk.ts b/src/ssn/decryption/decryptChunk.ts
index 8c60509..7b7fad0 100644
--- a/src/ssn/decryption/decryptChunk.ts
+++ b/src/ssn/decryption/decryptChunk.ts
@@ -13,7 +13,7 @@ export default function getDecryptor(decryptionKeys: [number, number, number]) {
       //decrypt byte
       const keyPart = (key2 | 2) & 0xFFFF;
       const decryptedByte = (keyPart * (keyPart ^ 1)) >>> 8;
-      curChar ^= decryptedByte & 0xFF;
+      curChar = (curChar ^ (decryptedByte & 0xFF)) & 0xFF;
 
       //update keys
       [key0, key1, key2] = updateKeys([key0, key1, key2], curChar);