diff --git a/module/assets/img/overpass.png b/module/assets/img/overpass.png
new file mode 100644
index 0000000..2c41621
Binary files /dev/null and b/module/assets/img/overpass.png differ
diff --git a/module/config/config.php b/module/config/config.php
index 1ff685b..f0c9e4b 100644
--- a/module/config/config.php
+++ b/module/config/config.php
@@ -271,6 +271,10 @@ $GLOBALS['LEAFLET_LAYERS'] = array
         'children' => false,
         'icon'     => 'system/modules/leaflet/assets/img/tile.png',
     ),
+    'overpass' => array(
+        'children' => false,
+        'icon'     => 'system/modules/leaflet/assets/img/overpass.png',
+    ),
 );
 
 /*
diff --git a/module/dca/tl_leaflet_layer.php b/module/dca/tl_leaflet_layer.php
index cc42fd3..f856829 100644
--- a/module/dca/tl_leaflet_layer.php
+++ b/module/dca/tl_leaflet_layer.php
@@ -792,9 +792,9 @@ $GLOBALS['TL_DCA']['tl_leaflet_layer'] = array
             'label'     => &$GLOBALS['TL_LANG']['tl_leaflet_layer']['cacheLifeTime'],
             'exclude'   => true,
             'inputType' => 'text',
-            'default'   => null,
-            'eval'      => array('maxlength' => 5, 'rgxp' => 'digit', 'tl_class' => 'w50', 'nullIfEmpty' => true),
-            'sql'       => "int(9) NOT NULL default '0'"
+            'default'   => 0,
+            'eval'      => array('maxlength' => 5, 'rgxp' => 'digit', 'tl_class' => 'w50'),
+            'sql'       => "int(10) unsigned NOT NULL default '0'"
         ),
         'overpassQuery'  => array
         (
@@ -815,7 +815,7 @@ $GLOBALS['TL_DCA']['tl_leaflet_layer'] = array
             'label'     => &$GLOBALS['TL_LANG']['tl_leaflet_layer']['overpassEndpoint'],
             'exclude'   => true,
             'inputType' => 'text',
-            'default'   => null,
+            'default'   => '',
             'eval'      => array('tl_class' => 'long'),
             'sql'       => "varchar(255) NOT NULL default ''"
         ),
@@ -850,7 +850,7 @@ $GLOBALS['TL_DCA']['tl_leaflet_layer'] = array
             'label'     => &$GLOBALS['TL_LANG']['tl_leaflet_layer']['minZoomIndicatorMessage'],
             'exclude'   => true,
             'inputType' => 'text',
-            'default'   => null,
+            'default'   => '',
             'eval'      => array('tl_class' => 'long'),
             'sql'       => "varchar(255) NOT NULL default ''"
         ),
@@ -859,7 +859,7 @@ $GLOBALS['TL_DCA']['tl_leaflet_layer'] = array
             'label'     => &$GLOBALS['TL_LANG']['tl_leaflet_layer']['minZoomIndicatorMessageNoLayer'],
             'exclude'   => true,
             'inputType' => 'text',
-            'default'   => null,
+            'default'   => '',
             'eval'      => array('tl_class' => 'long'),
             'sql'       => "varchar(255) NOT NULL default ''"
         ),
diff --git a/src/Netzmacht/Contao/Leaflet/Mapper/Layer/OverpassLayerMapper.php b/src/Netzmacht/Contao/Leaflet/Mapper/Layer/OverpassLayerMapper.php
index ca6da15..1f9029d 100644
--- a/src/Netzmacht/Contao/Leaflet/Mapper/Layer/OverpassLayerMapper.php
+++ b/src/Netzmacht/Contao/Leaflet/Mapper/Layer/OverpassLayerMapper.php
@@ -31,6 +31,13 @@ class OverpassLayerMapper extends AbstractLayerMapper
      */
     protected static $type = 'overpass';
 
+    /**
+     * The definition class.
+     *
+     * @var string
+     */
+    protected static $definitionClass = 'Netzmacht\LeafletPHP\Plugins\OverpassLayer\OverpassLayer';
+
     /**
      * {@inheritdoc}
      */
@@ -39,9 +46,9 @@ class OverpassLayerMapper extends AbstractLayerMapper
         parent::initialize();
 
         $this->optionsBuilder
-            ->addOption('overpassQuery', 'query')
-            ->addConditionalOption('minZoom')
-            ->addConditionalOption('overpassEndpoint', 'endpoint');
+            ->addOption('query', 'overpassQuery')
+            ->addOption('minzoom', 'minZoom')
+            ->addOption('overpassEndpoint', 'endpoint');
     }
 
     /**
@@ -61,9 +68,9 @@ class OverpassLayerMapper extends AbstractLayerMapper
         $minZoomIndicatorOptions        = $definition->getMinZoomIndicatorOptions();
         $minZoomIndicatorOptionsBuilder = new OptionsBuilder();
         $minZoomIndicatorOptionsBuilder
-            ->addConditionalOption('minZoomIndicatorPosition', 'position')
-            ->addConditionalOption('minZoomIndicatorMessageNoLayer', 'minZoomMessageNoLayer')
-            ->addConditionalOption('minZoomIndicatorMessage', 'minZoomMessage');
+            ->addOption('position', 'minZoomIndicatorPosition')
+            ->addOption('minZoomMessageNoLayer', 'minZoomIndicatorMessageNoLayer')
+            ->addOption('minZoomMessage', 'minZoomIndicatorMessage');
 
         $minZoomIndicatorOptionsBuilder->build($minZoomIndicatorOptions, $model);