diff --git a/roles/lmn_exam/tasks/main.yml b/roles/lmn_exam/tasks/main.yml
index 838fd68..d5610c2 100644
--- a/roles/lmn_exam/tasks/main.yml
+++ b/roles/lmn_exam/tasks/main.yml
@@ -52,7 +52,7 @@
 
 - name: Append teacherPC to exam_destination_allowed_ipv4 addresses
   ansible.builtin.set_fact:
-    exam_destination_allowed_ipv4: "{{ exam_destination_allowed_ipv4 + [ ansible_default_ipv4.address[:-1] ~ exam_teacherpc_last_digit ] }}"
+    exam_destination_allowed_ipv4: "{{ exam_destination_allowed_ipv4 + [ ansible_default_ipv4.address.rsplit('.', 1)[0] ~ '.' ~ exam_teacherpc_last_digit ] }}"
   when:
     - exam_destination_allowed_ipv4 is defined
     - exam_destination_allowed_ipv4 | length > 0