diff --git a/centreon-plugins/centreon/common/fortinet/fortigate/snmp/mode/cpu.pm b/centreon-plugins/centreon/common/fortinet/fortigate/snmp/mode/cpu.pm
index 91185c599..245ce76e6 100644
--- a/centreon-plugins/centreon/common/fortinet/fortigate/snmp/mode/cpu.pm
+++ b/centreon-plugins/centreon/common/fortinet/fortigate/snmp/mode/cpu.pm
@@ -147,8 +147,9 @@ sub manage_selection {
         $cpu += $snmp_result->{$oid_fgProcessorUsage}->{$_};
     }
 
+    my $num_core = scalar(keys %{$self->{cpu_core}});
     $self->{cpu_avg} = {
-        average => ($i > 0) ? $cpu / $i : $snmp_result->{$oid_fgSysCpuUsage}->{$oid_fgSysCpuUsage . '.0'}
+        average => $num_core > 0 ? $cpu / $num_core : $snmp_result->{$oid_fgSysCpuUsage}->{$oid_fgSysCpuUsage . '.0'}
     };
 
     if (defined($self->{option_results}->{cluster})) {