Divide by zero error on 100% discount

I’m getting a divide by zero warning when I apply a 100% discount:

Warning: Division by zero in /nas/content/live/universallife/wp-content/plugins/woocommerce-fixed-quantity/classes/client-fixed-quantity-price.php on line 203

public function filter_item_price($price, $cart_item, $cart_item_key)
        {
            if (empty($cart_item['data'])) {
                return $price;
            }

            $_product = apply_filters('woocommerce_cart_item_product', $cart_item['data'], $cart_item, $cart_item_key);
            $productId = WoofixUtility::getActualId($_product);
            $fixedPriceData = WoofixUtility::isFixedQtyPrice($productId);
            if ($fixedPriceData !== false) {
                $discount = 0;
                foreach ($fixedPriceData['woofix'] as $disc) {
                    if ($disc['woofix_qty'] == $cart_item['quantity']) {
                        $discount = $disc['woofix_disc'];
                    }
                }

                $itemPrice = $_product->get_price();
                $discprice = wc_price($itemPrice);

//this is line 203
                $oldprice = ($itemPrice * 100) / (100 - $discount);
//this is line 203^^
                $oldprice = wc_price($oldprice);
                if ($oldprice == $discprice) {
                    $price = "<span class='discount-info'><span class='new-price'>$discprice</span></span>";

                } else {
                    $price = "<span class='discount-info'>" .
                        "<span class='old-price'><del>$oldprice</del></span>&nbsp;" .
                        "<span class='new-price'><strong>$discprice</strong></span></span>";
                }
            }

            return $price;
        }