diff --git a/classes/PluginWonderfulWidget.php b/classes/PluginWonderfulWidget.php
index 42d9436..60bb1d7 100644
--- a/classes/PluginWonderfulWidget.php
+++ b/classes/PluginWonderfulWidget.php
@@ -1,58 +1,60 @@
 <?php
 
-class PluginWonderfulWidget extends WP_Widget {
-	function PluginWonderfulWidget() {
-		$widget_options = array(
-		  'classname' => 'plugin-wonderful',
-			'description' => __('A widget for adding your Project Wonderful advertisements', 'plugin-wonderful')
-		);
-		
-		$control_options = array(
-		  'id_base' => 'plugin-wonderful'
-		);
-		
-		$this->WP_Widget('plugin-wonderful', __('Plugin Wonderful', 'plugin-wonderful'), $widget_options, $control_options);
-	}
-	
-	function widget($args, $instance) {
-    global $plugin_wonderful;
-    $plugin_wonderful->_render_adbox($instance['adboxid'], $instance['center']);
-  }
-  
-  function form($instance) {
-    global $plugin_wonderful;
-    
-    if ($plugin_wonderful->publisher_info !== false) {
-      echo '<p>';
-        echo 'Select an adbox:<br />';
-        foreach ($plugin_wonderful->publisher_info->adboxes as $box) {
-          echo '<label>';
-            echo '<input type="radio" name="'
-                 . $this->get_field_name('adboxid')
-                 . '" value="'
-                 . $box->adboxid
-                 . '" '
-                 . (($instance['adboxid'] == $box->adboxid) ? 'checked="checked"' : "")
-                 . ' />';
-            echo $box->adtype . " " . $box->dimensions . " (" . $box->adboxid . ")";
-          echo "</label>";
-          echo "<br />";
-        }
-      echo '</p>';
+if (class_exists('WP_Widget')) {
+  class PluginWonderfulWidget extends WP_Widget {
+    function PluginWonderfulWidget() {
+      $widget_options = array(
+        'classname' => 'plugin-wonderful',
+        'description' => __('A widget for adding your Project Wonderful advertisements', 'plugin-wonderful')
+      );
       
-      echo '<p>';
-        echo '<label>';
-          echo '<input type="checkbox" value="1" name="' . $this->get_field_name('center') . '" ' . (($instance['center'] == 1) ? 'checked="checked"' : "") . ' /> ';
-          echo 'Wrap ad in &lt;center&gt; tags';
-        echo '</label>';
-      echo '</p>';
+      $control_options = array(
+        'id_base' => 'plugin-wonderful'
+      );
+      
+      $this->WP_Widget('plugin-wonderful', __('Plugin Wonderful', 'plugin-wonderful'), $widget_options, $control_options);
+    }
+    
+    function widget($args, $instance) {
+      global $plugin_wonderful;
+      $plugin_wonderful->_render_adbox($instance['adboxid'], $instance['center']);
+    }
+    
+    function form($instance) {
+      global $plugin_wonderful;
+      
+      if ($plugin_wonderful->publisher_info !== false) {
+        echo '<p>';
+          echo 'Select an adbox:<br />';
+          foreach ($plugin_wonderful->publisher_info->adboxes as $box) {
+            echo '<label>';
+              echo '<input type="radio" name="'
+                   . $this->get_field_name('adboxid')
+                   . '" value="'
+                   . $box->adboxid
+                   . '" '
+                   . (($instance['adboxid'] == $box->adboxid) ? 'checked="checked"' : "")
+                   . ' />';
+              echo $box->adtype . " " . $box->dimensions . " (" . $box->adboxid . ")";
+            echo "</label>";
+            echo "<br />";
+          }
+        echo '</p>';
+        
+        echo '<p>';
+          echo '<label>';
+            echo '<input type="checkbox" value="1" name="' . $this->get_field_name('center') . '" ' . (($instance['center'] == 1) ? 'checked="checked"' : "") . ' /> ';
+            echo 'Wrap ad in &lt;center&gt; tags';
+          echo '</label>';
+        echo '</p>';
+      }
+    }
+    
+    function update($new_instance, $old_instance) {
+      $instance = $new_instance;
+      if (!isset($instance['center'])) { $instance['center'] = 0; }
+      return $instance;
     }
-  }
-  
-  function update($new_instance, $old_instance) {
-    $instance = $new_instance;
-    if (!isset($instance['center'])) { $instance['center'] = 0; }
-    return $instance;
   }
 }
 
diff --git a/plugin-wonderful.php b/plugin-wonderful.php
index cf7693f..8fdd19f 100644
--- a/plugin-wonderful.php
+++ b/plugin-wonderful.php
@@ -34,7 +34,9 @@ define('PLUGIN_WONDERFUL_UPDATE_TIME', 60 * 60 * 12); // every 12 hours
 $plugin_wonderful = new PluginWonderful();
 
 function __plugin_wonderful_load_widgets() {
-  register_widget('PluginWonderfulWidget');
+  if (class_exists('WP_Widget')) {
+    register_widget('PluginWonderfulWidget');
+  }
 }
 
 add_action('admin_menu', array($plugin_wonderful, 'set_up_menu'));