diff --git block_class.module block_class.module
index 3a5f45b..079c865 100644
--- block_class.module
+++ block_class.module
@@ -10,6 +10,27 @@ function block_class_preprocess_block(&$vars) {
 }
 
 
+/*
+ * Extend panel block's classes with any user defined classes.
+ * Implements hook_preprocess_hook()
+ */
+function block_class_preprocess_panels_pane(&$vars) {
+  if ($vars['pane']->type != 'block') {
+    return;
+  }
+  // Infer the block's $module and $delta from the pane subtype.
+  $block_parts = explode('-', $vars['pane']->subtype);
+  // Load the block based on the block parts.
+  $block = block_load($block_parts[0], $block_parts[1]);
+  // Return block_class classes as string.
+  $css_class = block_class($block);
+  // Add a generic module type block class.
+  $vars['classes_array'][] = drupal_html_class('block-' . $block->module);
+  // Add $css_class to the $classes_array.
+  $vars['classes_array'][] = $css_class;
+}
+
+
 /**
  * Return classes as string
  */