diff --git a/isoimagewriter/isoverifier.cpp b/isoimagewriter/isoverifier.cpp
--- a/isoimagewriter/isoverifier.cpp
+++ b/isoimagewriter/isoverifier.cpp
@@ -29,7 +29,7 @@
 #include <QGpgME/ImportJob>
 #include <gpgme++/verificationresult.h>
 #include <gpgme++/importresult.h>
-
+#include <QVector>
 #include <KLocalizedString>
 
 IsoVerifier::IsoVerifier(const QString &filePath)
@@ -145,10 +145,12 @@
         m_error = i18n("Could not open ISO image");
         emit finished(m_isIsoValid, m_error); return;
     }
-    QByteArray isoData = isoFile.readAll();
+
+    std::vector<char> isoData;
+    isoFile.read(isoData.data(),1024);
 
     QGpgME::VerifyDetachedJob *job = QGpgME::openpgp()->verifyDetachedJob();
-    GpgME::VerificationResult result = job->exec(signatureData, isoData);
+    GpgME::VerificationResult result = job->exec(signatureData, isoData.data());
     GpgME::Signature signature = result.signature(0);
 
     if (signature.summary() == GpgME::Signature::None