diff --git a/d6_compat.inc b/d6_compat.inc
index 6303e46..76b6707 100644
--- a/d6_compat.inc
+++ b/d6_compat.inc
@@ -412,6 +412,13 @@ function _advanced_forum_build_preprocess($hook) {
   // Add all modules so they can intervene with their own preprocessors. This allows them
   // to provide preprocess functions even if they are not the owner of the current hook.
   $prefixes += module_list();
+  // Some modules in d5 already have functions that look like preprocess hooks.
+  // We black list those from being added.
+  $blacklist = array('search');
+
+  foreach ($blacklist as $module) {
+    unset($prefixes[array_search($module, $prefixes)]);
+  }
 
   foreach ($prefixes as $prefix) {
     if (function_exists($prefix .'_preprocess')) {