diff --git a/app/Http/Controllers/SignupController.php b/app/Http/Controllers/SignupController.php
index d471bf33..bf5c0e2b 100644
--- a/app/Http/Controllers/SignupController.php
+++ b/app/Http/Controllers/SignupController.php
@@ -38,7 +38,7 @@ class SignupController extends Controller
      */
     public function getSignup($code = null)
     {
-        if (is_null($code)) {
+        if ($code !== null) {
             throw new NotFoundHttpException();
         }
 
@@ -65,7 +65,7 @@ class SignupController extends Controller
      */
     public function postSignup($code = null)
     {
-        if (is_null($code)) {
+        if ($code !== null) {
             throw new NotFoundHttpException();
         }
 
diff --git a/app/Http/Controllers/SubscribeController.php b/app/Http/Controllers/SubscribeController.php
index 59d5cd17..72f921ae 100644
--- a/app/Http/Controllers/SubscribeController.php
+++ b/app/Http/Controllers/SubscribeController.php
@@ -71,7 +71,7 @@ class SubscribeController extends Controller
      */
     public function getVerify($code = null)
     {
-        if (is_null($code)) {
+        if ($code !== null) {
             throw new NotFoundHttpException();
         }
 
@@ -96,7 +96,7 @@ class SubscribeController extends Controller
      */
     public function getUnsubscribe($code = null)
     {
-        if (is_null($code)) {
+        if ($code !== null) {
             throw new NotFoundHttpException();
         }
 
diff --git a/app/Models/Invite.php b/app/Models/Invite.php
index 84bf5d93..2a4ea330 100644
--- a/app/Models/Invite.php
+++ b/app/Models/Invite.php
@@ -62,6 +62,6 @@ class Invite extends Model
      */
     public function claimed()
     {
-        return !is_null($this->claimed_at);
+        return $this->claimed_at !== null;
     }
 }
diff --git a/app/Models/Subscriber.php b/app/Models/Subscriber.php
index bbd3030f..4d3adbe5 100644
--- a/app/Models/Subscriber.php
+++ b/app/Models/Subscriber.php
@@ -69,7 +69,7 @@ class Subscriber extends Model implements HasPresenter
      */
     public function verified()
     {
-        return !is_null($this->verified_at);
+        return $this->verified_at !== null;
     }
 
     /**