diff --git a/includes/module.inc b/includes/module.inc
index 2e25108..c57f659 100644
--- a/includes/module.inc
+++ b/includes/module.inc
@@ -684,7 +684,7 @@ function module_hook($module, $hook) {
   // If the hook implementation does not exist, check whether it may live in an
   // optional include file registered via hook_hook_info().
   $hook_info = module_hook_info();
-  if (isset($hook_info[$hook]['group'])) {
+  if (isset($hook_info[$hook]['group']) && module_exists($module)) {
     module_load_include('inc', $module, $module . '.' . $hook_info[$hook]['group']);
     if (function_exists($function)) {
       return TRUE;