diff --git a/block_class.module b/block_class.module
index 22b2022..03dda74 100644
--- a/block_class.module
+++ b/block_class.module
@@ -44,7 +44,7 @@ function block_class_preprocess_panels_pane(&$vars) {
     return;
   }
   // Infer the block's $module and $delta from the pane subtype.
-  $block_parts = explode('-', $vars['pane']->subtype);
+  $block_parts = explode('-', $vars['pane']->subtype, 2);
   // Load the block based on the block parts.
   $block = block_load($block_parts[0], $block_parts[1]);
   // Add a generic 'module type' pane class.