diff --git a/PVE/Jobs/VZDump.pm b/PVE/Jobs/VZDump.pm
index 92b81147..c757eea1 100644
--- a/PVE/Jobs/VZDump.pm
+++ b/PVE/Jobs/VZDump.pm
@@ -72,6 +72,12 @@ sub run {
 	delete $conf->{$opt} if !defined($props->{$opt});
     }
 
+    # fixup prune-backups, we get it decoded but want it as string parameter
+    $conf->{'prune-backups'} = PVE::JSONSchema::print_property_string(
+	$conf->{'prune-backups'},
+	'prune-backups',
+    ) if $conf->{'prune-backups'} && ref($conf->{'prune-backups'}) eq 'HASH';
+
     $conf->{quiet} = 1; # do not write to stdout/stderr
 
     PVE::Cluster::cfs_update(); # refresh vmlist