diff --git a/app/Billing/FakePaymentGateway.php b/app/Billing/FakePaymentGateway.php
index 0e91109..668ef62 100644
--- a/app/Billing/FakePaymentGateway.php
+++ b/app/Billing/FakePaymentGateway.php
@@ -20,7 +20,9 @@ class FakePaymentGateway implements PaymentGateway
     public function charge($amount, $token)
     {
         if ($this->beforeFirstChargeCallback !== null) {
-            $this->beforeFirstChargeCallback->__invoke($this);
+            $callback = $this->beforeFirstChargeCallback;
+            $this->beforeFirstChargeCallback = null;
+            $callback($this);
         }
 
         if ($token !== $this->getValidTestToken()) {
diff --git a/tests/features/PurchaseTicketsTest.php b/tests/features/PurchaseTicketsTest.php
index 177d985..5ee734c 100644
--- a/tests/features/PurchaseTicketsTest.php
+++ b/tests/features/PurchaseTicketsTest.php
@@ -105,6 +105,8 @@ class PurchaseTicketsTest extends TestCase
     /** @test */
     function cannot_purchase_tickets_another_customer_is_already_trying_to_purchase()
     {
+        $this->disableExceptionHandling();
+
         $concert = factory(Concert::class)->states('published')->create([
             'ticket_price' => 1200
         ])->addTickets(3);
diff --git a/tests/unit/Billing/FakePaymentGatewayTest.php b/tests/unit/Billing/FakePaymentGatewayTest.php
index 192fe6f..a5caccb 100644
--- a/tests/unit/Billing/FakePaymentGatewayTest.php
+++ b/tests/unit/Billing/FakePaymentGatewayTest.php
@@ -35,15 +35,16 @@ class FakePaymentGatewayTest extends TestCase
     function running_a_hook_before_the_first_charge()
     {
         $paymentGateway = new FakePaymentGateway;
-        $callbackRan = false;
+        $timesCallbackRan = 0;
 
-        $paymentGateway->beforeFirstCharge(function ($paymentGateway) use (&$callbackRan) {
-            $callbackRan = true;
-            $this->assertEquals(0, $paymentGateway->totalCharges());
+        $paymentGateway->beforeFirstCharge(function ($paymentGateway) use (&$timesCallbackRan) {
+            $timesCallbackRan++;
+            $paymentGateway->charge(2500, $paymentGateway->getValidTestToken());
+            $this->assertEquals(2500, $paymentGateway->totalCharges());
         });
 
         $paymentGateway->charge(2500, $paymentGateway->getValidTestToken());
-        $this->assertTrue($callbackRan);
-        $this->assertEquals(2500, $paymentGateway->totalCharges());
+        $this->assertEquals(1, $timesCallbackRan);
+        $this->assertEquals(5000, $paymentGateway->totalCharges());
     }
 }