diff --git a/lib/extern/modules/ExternModuleTemplatePersondetails.class.php b/lib/extern/modules/ExternModuleTemplatePersondetails.class.php
index 34e91afc3589f321e135281333e8621e289304b7..4f6fb52b9f19c2988f1c90a500f5f0caf92e897b 100644
--- a/lib/extern/modules/ExternModuleTemplatePersondetails.class.php
+++ b/lib/extern/modules/ExternModuleTemplatePersondetails.class.php
@@ -657,7 +657,7 @@ class ExternModuleTemplatePersondetails extends ExternModule {
         }
 
         // Is a semester switch defined?
-        $week_offset = $module->config->getValue('PersondetailsLectures', 'semswitch');
+        $week_offset = $this->config->getValue('PersondetailsLectures', 'semswitch');
         if (ctype_digit($week_offset)) {
             $switch_time = strtotime("+{$week_offset} weeks 0:00:00");
         } else {