diff --git a/roles/base/tasks/base.yml b/roles/base/tasks/base.yml
index 1ac7754..82bb333 100644
--- a/roles/base/tasks/base.yml
+++ b/roles/base/tasks/base.yml
@@ -39,13 +39,13 @@
   apt: pkg={{ item }} state=absent purge=yes
   with_items: "{{ base_client_delpkg }}"
   sudo: yes
-  when: role == 'client' and base_client_delpkg is defined 
+  when: role == 'client' and base_client_delpkg|length > 0
 
 - name: Rimozione pacchetti installati ruolo docenti
   apt: pkg={{ item }} state=absent purge=yes
   with_items: "{{ base_docenti_delpkg }}"
   sudo: yes
-  when: role == 'docenti' and base_docenti_delpkg is defined
+  when: role == 'docenti' and base_docenti_delpkg|length > 0
 
 - name: Rimozione pacchetti non più necessari
   shell: apt-get -y autoremove
@@ -63,13 +63,13 @@
   apt: pkg={{ item }} state=present
   with_items: "{{ base_client_addpkg }}"
   sudo: yes
-  when: role == 'client' and base_client_addpkg is defined
+  when: role == 'client' and base_client_addpkg|length > 0
 
 - name: Installazione pacchetti installati ruolo docenti
   apt: pkg={{ item }} state=present
   with_items: "{{ base_docenti_addpkg }}"
   sudo: yes
-  when: role == 'docenti' and base_docenti_addpkg is defined
+  when: role == 'docenti' and base_docenti_addpkg|length > 0
 
 - name: Aggiungo VirtualBox Guest Additions, se necessario
   apt: pkg=virtualbox-guest-dkms state=present