diff --git a/.travis.yml b/.travis.yml
index 16578c6..27e83fe 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -28,6 +28,10 @@ matrix:
           php: 7.3
           env: DEPENDENCIES="roave/backward-compatibility-check"
           script: ./vendor/bin/roave-backward-compatibility-check || true
+        - name: PHPStan
+          php: 7.2
+          env: DEPENDENCIES="phpstan/phpstan phpstan/phpstan-webmozart-assert"
+          script: ./vendor/bin/phpstan analyse src
 
 before_install:
   - if [[ "$PREFER_COVERAGE" = true ]] && [[ "$TRAVIS_PULL_REQUEST" = false ]]; then TEST_COMMAND="composer test-coverage" COVERAGE=true; fi
diff --git a/phpstan.neon b/phpstan.neon
new file mode 100644
index 0000000..0ae4ea2
--- /dev/null
+++ b/phpstan.neon
@@ -0,0 +1,5 @@
+parameters:
+	level: 5
+
+includes:
+	- vendor/phpstan/phpstan-webmozart-assert/extension.neon
diff --git a/src/Api/HttpApi.php b/src/Api/HttpApi.php
index 31ed4fb..d63a90d 100644
--- a/src/Api/HttpApi.php
+++ b/src/Api/HttpApi.php
@@ -34,7 +34,7 @@ abstract class HttpApi
     protected $httpClient;
 
     /**
-     * @var null|Hydrator
+     * @var Hydrator|null
      */
     protected $hydrator;
 
diff --git a/src/Mailgun.php b/src/Mailgun.php
index eeaf74f..04cacbb 100644
--- a/src/Mailgun.php
+++ b/src/Mailgun.php
@@ -25,7 +25,7 @@ use Psr\Http\Message\ResponseInterface;
 final class Mailgun
 {
     /**
-     * @var null|string
+     * @var string|null
      */
     private $apiKey;
 
diff --git a/src/Model/Tag/CountryResponse.php b/src/Model/Tag/CountryResponse.php
index d650d2c..aae3b7c 100644
--- a/src/Model/Tag/CountryResponse.php
+++ b/src/Model/Tag/CountryResponse.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * Copyright (C) 2013 Mailgun
  *
@@ -26,16 +28,10 @@ final class CountryResponse implements ApiResponse
      */
     private $tag;
 
-    /**
-     * @param string $message
-     */
     private function __construct()
     {
     }
 
-    /**
-     * @param array $data
-     */
     public static function create(array $data): self
     {
         $model = new self();
diff --git a/src/Model/Tag/DeviceResponse.php b/src/Model/Tag/DeviceResponse.php
index d2dabdc..472eae8 100644
--- a/src/Model/Tag/DeviceResponse.php
+++ b/src/Model/Tag/DeviceResponse.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * Copyright (C) 2013 Mailgun
  *
@@ -26,16 +28,10 @@ final class DeviceResponse implements ApiResponse
      */
     private $tag;
 
-    /**
-     * @param string $message
-     */
     private function __construct()
     {
     }
 
-    /**
-     * @param array $data
-     */
     public static function create(array $data): self
     {
         $model = new self();
diff --git a/src/Model/Tag/ProviderResponse.php b/src/Model/Tag/ProviderResponse.php
index 07493f7..8427778 100644
--- a/src/Model/Tag/ProviderResponse.php
+++ b/src/Model/Tag/ProviderResponse.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /*
  * Copyright (C) 2013 Mailgun
  *
@@ -26,16 +28,10 @@ final class ProviderResponse implements ApiResponse
      */
     private $tag;
 
-    /**
-     * @param string $message
-     */
     private function __construct()
     {
     }
 
-    /**
-     * @param array $data
-     */
     public static function create(array $data): self
     {
         $model = new self();