diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index 7778fb86..2414fd86 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -5605,7 +5605,7 @@ sub qemu_img_convert {
 	my $dst_path = PVE::Storage::path($storecfg, $dst_volid);
 
 	my $cmd = [];
-	push @$cmd, '/usr/bin/qemu-img', 'convert', '-t', 'writeback', '-p', '-n';
+	push @$cmd, '/usr/bin/qemu-img', 'convert', '-p', '-n';
 	push @$cmd, '-s', $snapname if($snapname && $src_format eq "qcow2");
 	push @$cmd, '-f', $src_format, '-O', $dst_format, $src_path;
 	if ($is_zero_initialized) {