Client_HasWeapon non-functional with weapon_m4a1_silencer (csgo)

[DrKittens]

if(Client_HasWeapon(client, "weapon_m4a1_silencer"))
{
ReplyToCommand(client, "You are holding an m4a1-s");
return Plugin_Handled;
}
else
{
ReplyToCommand(client, "You are not holding an m4a1-s");
return Plugin_Handled;
}

Will always return false even when the condition is met.