--- rxvt-unicode/src/perl/background	2012/06/10 13:32:55	1.46
+++ rxvt-unicode/src/perl/background	2012/06/10 15:01:14	1.48
@@ -798,7 +798,7 @@
 
    my $img = eval { $self->{expr}->() };
    warn $@ if $@;#d#
-   die if !UNIVERSAL::isa $img, "urxvt::img";
+   die "background-expr did not return an image.\n" if !UNIVERSAL::isa $img, "urxvt::img";
 
    $state->{size_sensitive} = 1
       if $img->repeat_mode != urxvt::RepeatNormal;
@@ -858,13 +858,16 @@
 sub on_start {
    my ($self) = @_;
 
-   my $expr = $self->x_resource ("background.expr")
+   my $expr = $self->x_resource ("%.expr")
       or return;
 
+   $self->has_render
+      or die "background extension needs RENDER extension 0.10 or higher, ignoring background-expr.\n";
+
    $self->set_expr (parse_expr $expr);
-   $self->{border} = $self->x_resource_boolean ("background.border");
+   $self->{border} = $self->x_resource_boolean ("%.border");
 
-   $MIN_INTERVAL = $self->x_resource ("background.interval");
+   $MIN_INTERVAL = $self->x_resource ("%.interval");
 
    ()
 }