diff --git a/admin/roles/classes/define_role_table_advanced.php b/admin/roles/classes/define_role_table_advanced.php
index c0e3d8d5ab8af..6fb58c6b25ff9 100644
--- a/admin/roles/classes/define_role_table_advanced.php
+++ b/admin/roles/classes/define_role_table_advanced.php
@@ -158,19 +158,19 @@ public function read_submitted_permissions() {
         // Allowed roles.
         $allow = optional_param_array('allowassign', null, PARAM_INT);
         if (!is_null($allow)) {
-            $this->allowassign = $allow;
+            $this->allowassign = array_filter($allow);
         }
         $allow = optional_param_array('allowoverride', null, PARAM_INT);
         if (!is_null($allow)) {
-            $this->allowoverride = $allow;
+            $this->allowoverride = array_filter($allow);
         }
         $allow = optional_param_array('allowswitch', null, PARAM_INT);
         if (!is_null($allow)) {
-            $this->allowswitch = $allow;
+            $this->allowswitch = array_filter($allow);
         }
         $allow = optional_param_array('allowview', null, PARAM_INT);
         if (!is_null($allow)) {
-            $this->allowview = $allow;
+            $this->allowview = array_filter($allow);
         }
 
         // Now read the permissions for each capability.
@@ -619,7 +619,9 @@ protected function get_allow_role_control($type) {
         if ($this->roleid == 0) {
             $options[-1] = get_string('thisnewrole', 'core_role');
         }
-        return html_writer::select($options, 'allow'.$type.'[]', $selected, false, array('multiple' => 'multiple',
+        return
+            html_writer::empty_tag('input', array('type' => 'hidden', 'name' => 'allow'.$type.'[]', 'value' => "")) .
+            html_writer::select($options, 'allow'.$type.'[]', $selected, false, array('multiple' => 'multiple',
             'size' => 10, 'class' => 'form-control'));
     }