diff --git a/iso/iso.cpp b/iso/iso.cpp
--- a/iso/iso.cpp
+++ b/iso/iso.cpp
@@ -357,7 +357,13 @@
     totalSize(size);
     if (!size) mimeType("application/x-zerosize");
 
-    if (size && !m_isoFile->device()->isOpen()) m_isoFile->device()->open(QIODevice::ReadOnly);
+    if (size && !m_isoFile->device()->isOpen()) {
+        m_isoFile->device()->open(QIODevice::ReadOnly);
+
+        // seek(0) ensures integrity with the QIODevice's built-in buffer
+        // see bug #372023 for details
+        m_isoFile->device()->seek(0);
+    }
 
     if (zlib) {
         fileData = isoFileEntry->dataAt(0, sizeof(compressed_file_header));
diff --git a/iso/kiso.cpp b/iso/kiso.cpp
--- a/iso/kiso.cpp
+++ b/iso/kiso.cpp
@@ -212,6 +212,10 @@
 
     QIODevice* dev = (static_cast<KIso*>(udata))->device();
 
+    // seek(0) ensures integrity with the QIODevice's built-in buffer
+    // see bug #372023 for details
+    dev->seek(0);
+
     if (dev->seek((qint64)start << (qint64)11)) {
         if ((dev->read(buf, len << 11u)) != -1) return (len);
     }