diff --git a/src/uas/QGCUASFileManager.cc b/src/uas/QGCUASFileManager.cc
index 6ef7d19cb7146524cb12d2e36e535ef46e0131f9..65fd98ee5270b2bbbd067249111bbefdde31c88e 100644
--- a/src/uas/QGCUASFileManager.cc
+++ b/src/uas/QGCUASFileManager.cc
@@ -107,7 +107,7 @@ void QGCUASFileManager::_openAckResponse(Request* openAck)
     
     // File length comes back in data
     Q_ASSERT(openAck->hdr.size == sizeof(uint32_t));
-    uint32_t fileLength = *((uint32_t*)openAck->data);
+    uint32_t fileLength = *((uint32_t*)&openAck->data[0]);
     emit openFileLength(fileLength);
 
     _readOffset = 0;                // Start reading at beginning of file