diff --git a/lib/Gscan2pdf/Dialog/Scan/Sane.pm b/lib/Gscan2pdf/Dialog/Scan/Sane.pm
index 8d35b05..647952d 100644
--- a/lib/Gscan2pdf/Dialog/Scan/Sane.pm
+++ b/lib/Gscan2pdf/Dialog/Scan/Sane.pm
@@ -728,6 +728,7 @@ sub set_option_widget {
         elsif ( defined $widget ) {
             given ($widget) {
                 when ( $widget->isa('Gtk2::CheckButton') ) {
+                    if ( $val eq '' ) { $val = 0 }
                     if ( $widget->get_active != $val ) {
                         $widget->set_active($val);
                         return $i;
diff --git a/lib/Gscan2pdf/Frontend/Sane.pm b/lib/Gscan2pdf/Frontend/Sane.pm
index 6930989..cc580f8 100644
--- a/lib/Gscan2pdf/Frontend/Sane.pm
+++ b/lib/Gscan2pdf/Frontend/Sane.pm
@@ -422,6 +424,8 @@ sub _thread_get_options {
 
 sub _thread_set_option {
     my ( $self, $index, $value, $new_options ) = @_;
+    my $opt = $self->{device_handle}->get_option_descriptor($index);
+    if ( $opt->{type} == SANE_TYPE_BOOL and $value eq '' ) { $value = 0 }
 
     # FIXME: Stringification to force this SV to have a PV slot.  This seems to
     # be necessary to get through Sane.pm's value checks.
@@ -430,7 +434,6 @@ sub _thread_set_option {
     my $info = $self->{device_handle}->set_option( $index, $value );
     if ( $logger->is_info ) {
         my $status = $Sane::STATUS;
-        my $opt    = $self->{device_handle}->get_option_descriptor($index);
         $logger->info(
 "sane_set_option $index ($opt->{name}) to $value returned status $status with info $info"
         );