diff --git a/src/decrypt/qmcMask.js b/src/decrypt/qmcMask.js
index 02097d4..0a2698e 100644
--- a/src/decrypt/qmcMask.js
+++ b/src/decrypt/qmcMask.js
@@ -115,7 +115,7 @@ export function QmcMaskDetectMflac(data) {
     for (let block_idx = 0; block_idx < search_len; block_idx += 128) {
         try {
             mask = new QmcMask(data.slice(block_idx, block_idx + 128));
-            if (!IsBytesEqual(FLAC_HEADER, mask.Decrypt(data.slice(0, FLAC_HEADER.length)))) break;
+            if (IsBytesEqual(FLAC_HEADER, mask.Decrypt(data.slice(0, FLAC_HEADER.length)))) break;
         } catch (e) {
         }
     }