diff --git a/src/qt/qt_mediamenu.cpp b/src/qt/qt_mediamenu.cpp
index 64f547272..3ee08879a 100644
--- a/src/qt/qt_mediamenu.cpp
+++ b/src/qt/qt_mediamenu.cpp
@@ -188,7 +188,7 @@ void MediaMenu::cassetteMount(const QString& filename, bool wp) {
 
     if (! filename.isEmpty()) {
         QByteArray filenameBytes = filename.toUtf8();
-        strncpy(cassette_fname, filenameBytes.data(), sizeof(cassette_fname));
+        strncpy(cassette_fname, filenameBytes.data(), sizeof(cassette_fname) - 1);
         pc_cas_set_fname(cassette, cassette_fname);
     }
 
diff --git a/src/qt/qt_settingsharddisks.cpp b/src/qt/qt_settingsharddisks.cpp
index 43cd3fc9c..df9c6b1dc 100644
--- a/src/qt/qt_settingsharddisks.cpp
+++ b/src/qt/qt_settingsharddisks.cpp
@@ -151,7 +151,7 @@ void SettingsHarddisks::save() {
         hdd[i].spt = idx.siblingAtColumn(ColumnSectors).data().toUInt();
 
         QByteArray fileName = idx.siblingAtColumn(ColumnFilename).data(Qt::UserRole).toString().toUtf8();
-        strncpy(hdd[i].fn, fileName.data(), sizeof(hdd[i].fn));
+        strncpy(hdd[i].fn, fileName.data(), sizeof(hdd[i].fn) - 1);
         hdd[i].priv = nullptr;
     }
 }
@@ -247,12 +247,14 @@ static void addDriveFromDialog(Ui::SettingsHarddisks* ui, const HarddiskDialog&
     QByteArray fn = dlg.fileName().toUtf8();
 
     hard_disk_t hd;
+    memset(&hd, 0, sizeof(hd));
+
     hd.bus = dlg.bus();
     hd.channel = dlg.channel();
     hd.tracks = dlg.cylinders();
     hd.hpc = dlg.heads();
     hd.spt = dlg.sectors();
-    strncpy(hd.fn, fn.data(), sizeof(hd.fn));
+    strncpy(hd.fn, fn.data(), sizeof(hd.fn) - 1);
 
     addRow(ui->tableView->model(), &hd);
     ui->tableView->resizeColumnsToContents();