diff --git a/PVE/API2/Qemu.pm b/PVE/API2/Qemu.pm
index d9ef201e..3ec31c26 100644
--- a/PVE/API2/Qemu.pm
+++ b/PVE/API2/Qemu.pm
@@ -328,6 +328,15 @@ my $create_disks = sub {
 	} elsif (defined($volname) && $volname eq 'cloudinit') {
 	    $storeid = $storeid // $default_storage;
 	    die "no storage ID specified (and no default storage)\n" if !$storeid;
+
+	    if (
+		my $ci_key = PVE::QemuConfig->has_cloudinit($conf, $ds)
+		|| PVE::QemuConfig->has_cloudinit($conf->{pending} || {}, $ds)
+		|| PVE::QemuConfig->has_cloudinit($res, $ds)
+	    ) {
+		die "$ds - cloud-init drive is already attached at '$ci_key'\n";
+	    }
+
 	    my $scfg = PVE::Storage::storage_config($storecfg, $storeid);
 	    my $name = "vm-$vmid-cloudinit";
 
@@ -424,6 +433,16 @@ my $create_disks = sub {
 		my ($vtype) = PVE::Storage::parse_volname($storecfg, $volid);
 		die "cannot use volume $volid - content type needs to be 'images' or 'iso'"
 		    if $vtype ne 'images' && $vtype ne 'iso';
+
+		if (PVE::QemuServer::Drive::drive_is_cloudinit($disk)) {
+		    if (
+			my $ci_key = PVE::QemuConfig->has_cloudinit($conf, $ds)
+			|| PVE::QemuConfig->has_cloudinit($conf->{pending} || {}, $ds)
+			|| PVE::QemuConfig->has_cloudinit($res, $ds)
+		    ) {
+			die "$ds - cloud-init drive is already attached at '$ci_key'\n";
+		    }
+		}
 	    }
 
 	    PVE::Storage::activate_volumes($storecfg, [ $volid ]) if $storeid;
diff --git a/PVE/QemuConfig.pm b/PVE/QemuConfig.pm
index b75227b5..482c7abd 100644
--- a/PVE/QemuConfig.pm
+++ b/PVE/QemuConfig.pm
@@ -521,4 +521,19 @@ sub __snapshot_rollback_get_unused {
 
 # END implemented abstract methods from PVE::AbstractConfig
 
+sub has_cloudinit {
+    my ($class, $conf, $skip) = @_;
+
+    my $found;
+
+    $class->foreach_volume($conf, sub {
+	my ($key, $volume) = @_;
+
+	return if ($skip && $skip eq $key) || $found;
+	$found = $key if PVE::QemuServer::Drive::drive_is_cloudinit($volume);
+    });
+
+    return $found;
+}
+
 1;