--- a/strongarm.install
+++ b/strongarm.install
@@ -21,6 +21,15 @@ function strongarm_enable() {
  * Transition Strongarm variables from code to the database.
  */
 function strongarm_update_7201() {
+  $modules = array('ctools');
+  module_enable($modules);
+
+  foreach ($modules as $module) {
+    if (!module_exists($module)) {
+      throw new DrupalUpdateException(t('Ctools is dependent of Strongarm. Please download them to sites/all/modules and run update.php again.'));
+    }
+  }
+
   module_load_include('module', 'strongarm');
   $variables = strongarm_vars_load(TRUE, TRUE);
   if (!empty($variables)) {