diff --git a/PVE/CLI/pvesm.pm b/PVE/CLI/pvesm.pm
index caac51b..d7591ee 100755
--- a/PVE/CLI/pvesm.pm
+++ b/PVE/CLI/pvesm.pm
@@ -752,10 +752,7 @@ __PACKAGE__->register_method ({
 	    storage => get_standard_option('pve-storage-id', {
 		completion => \&PVE::Storage::complete_storage_enabled,
             }),
-	    'prune-backups' => get_standard_option('prune-backups', {
-		description => "Use these retention options instead of those from the storage configuration.",
-		optional => 1,
-	    }),
+	    %{$PVE::Storage::Plugin::prune_backups_format},
 	    type => {
 		description => "Either 'qemu' or 'lxc'. Only consider backups for guests of this type.",
 		type => 'string',
@@ -813,6 +810,13 @@ __PACKAGE__->register_method ({
 
 	my $dryrun = extract_param($param, 'dry-run') ? 1 : 0;
 
+	my $keep_opts;
+	foreach my $keep (keys %{$PVE::Storage::Plugin::prune_backups_format}) {
+	    $keep_opts->{$keep} = extract_param($param, $keep) if defined($param->{$keep});
+	}
+	$param->{'prune-backups'} = PVE::JSONSchema::print_property_string(
+	    $keep_opts, $PVE::Storage::Plugin::prune_backups_format) if $keep_opts;
+
 	my $list = [];
 	if ($dryrun) {
 	    $list = PVE::API2::Storage::PruneBackups->dryrun($param);
diff --git a/PVE/Storage/Plugin.pm b/PVE/Storage/Plugin.pm
index 8a58ff4..5b337df 100644
--- a/PVE/Storage/Plugin.pm
+++ b/PVE/Storage/Plugin.pm
@@ -49,7 +49,7 @@ my %prune_option = (
     format_description => 'N',
 );
 
-my $prune_backups_format = {
+our $prune_backups_format = {
 	'keep-last' => {
 	    %prune_option,
 	    description => 'Keep the last <N> backups.',