diff --git a/lib/Github/Api/AcceptHeaderTrait.php b/lib/Github/Api/AcceptHeaderTrait.php
index e788fd1ca5e..3d22824fdba 100644
--- a/lib/Github/Api/AcceptHeaderTrait.php
+++ b/lib/Github/Api/AcceptHeaderTrait.php
@@ -9,6 +9,7 @@
  */
 trait AcceptHeaderTrait
 {
+    /** @var string */
     protected $acceptHeaderValue;
 
     protected function get($path, array $parameters = [], array $requestHeaders = [])
diff --git a/lib/Github/Client.php b/lib/Github/Client.php
index 2052461335d..9b27c346677 100644
--- a/lib/Github/Client.php
+++ b/lib/Github/Client.php
@@ -333,6 +333,8 @@ public function api($name)
      * @param null|string $authMethod   One of the AUTH_* class constants
      *
      * @throws InvalidArgumentException If no authentication method was given
+     *
+     * @return void
      */
     public function authenticate($tokenOrLogin, $password = null, $authMethod = null)
     {
@@ -357,6 +359,8 @@ public function authenticate($tokenOrLogin, $password = null, $authMethod = null
      * Sets the URL of your GitHub Enterprise instance.
      *
      * @param string $enterpriseUrl URL of the API in the form of http(s)://hostname
+     *
+     * @return void
      */
     private function setEnterpriseUrl($enterpriseUrl)
     {
@@ -381,6 +385,8 @@ public function getApiVersion()
      *
      * @param CacheItemPoolInterface $cachePool
      * @param array                  $config
+     *
+     * @return void
      */
     public function addCache(CacheItemPoolInterface $cachePool, array $config = [])
     {
@@ -389,6 +395,8 @@ public function addCache(CacheItemPoolInterface $cachePool, array $config = [])
 
     /**
      * Remove the cache plugin.
+     *
+     * @return void
      */
     public function removeCache()
     {
@@ -397,8 +405,7 @@ public function removeCache()
 
     /**
      * @param string $name
-     *
-     * @throws BadMethodCallException
+     * @param array  $args
      *
      * @return ApiInterface
      */
diff --git a/lib/Github/Exception/ApiLimitExceedException.php b/lib/Github/Exception/ApiLimitExceedException.php
index 0283175f19b..f2dd9b874d6 100644
--- a/lib/Github/Exception/ApiLimitExceedException.php
+++ b/lib/Github/Exception/ApiLimitExceedException.php
@@ -9,9 +9,17 @@
  */
 class ApiLimitExceedException extends RuntimeException
 {
+    /** @var int */
     private $limit;
+    /** @var int */
     private $reset;
 
+    /**
+     * @param int             $limit
+     * @param int             $reset
+     * @param int             $code
+     * @param \Throwable|null $previous
+     */
     public function __construct($limit = 5000, $reset = 1800, $code = 0, $previous = null)
     {
         $this->limit = (int) $limit;
@@ -20,11 +28,17 @@ public function __construct($limit = 5000, $reset = 1800, $code = 0, $previous =
         parent::__construct(sprintf('You have reached GitHub hourly limit! Actual limit is: %d', $limit), $code, $previous);
     }
 
+    /**
+     * @return int
+     */
     public function getLimit()
     {
         return $this->limit;
     }
 
+    /**
+     * @return int
+     */
     public function getResetTime()
     {
         return $this->reset;
diff --git a/lib/Github/Exception/MissingArgumentException.php b/lib/Github/Exception/MissingArgumentException.php
index f5e46ef68aa..7a14bb51ae7 100644
--- a/lib/Github/Exception/MissingArgumentException.php
+++ b/lib/Github/Exception/MissingArgumentException.php
@@ -9,6 +9,11 @@
  */
 class MissingArgumentException extends ErrorException
 {
+    /**
+     * @param string|array    $required
+     * @param int             $code
+     * @param \Throwable|null $previous
+     */
     public function __construct($required, $code = 0, $previous = null)
     {
         if (is_string($required)) {
diff --git a/lib/Github/Exception/TwoFactorAuthenticationRequiredException.php b/lib/Github/Exception/TwoFactorAuthenticationRequiredException.php
index 6f93fe40b14..0e63b277ce6 100644
--- a/lib/Github/Exception/TwoFactorAuthenticationRequiredException.php
+++ b/lib/Github/Exception/TwoFactorAuthenticationRequiredException.php
@@ -4,14 +4,23 @@
 
 class TwoFactorAuthenticationRequiredException extends RuntimeException
 {
+    /** @var string */
     private $type;
 
+    /**
+     * @param string          $type
+     * @param int             $code
+     * @param \Throwable|null $previous
+     */
     public function __construct($type, $code = 0, $previous = null)
     {
         $this->type = $type;
         parent::__construct('Two factor authentication is enabled on this account', $code, $previous);
     }
 
+    /**
+     * @return string
+     */
     public function getType()
     {
         return $this->type;
diff --git a/lib/Github/HttpClient/Builder.php b/lib/Github/HttpClient/Builder.php
index 3b05b8fecc5..90263cb6632 100644
--- a/lib/Github/HttpClient/Builder.php
+++ b/lib/Github/HttpClient/Builder.php
@@ -113,6 +113,8 @@ public function getHttpClient()
      * Add a new plugin to the end of the plugin chain.
      *
      * @param Plugin $plugin
+     *
+     * @return void
      */
     public function addPlugin(Plugin $plugin)
     {
@@ -124,6 +126,8 @@ public function addPlugin(Plugin $plugin)
      * Remove a plugin by its fully qualified class name (FQCN).
      *
      * @param string $fqcn
+     *
+     * @return void
      */
     public function removePlugin($fqcn)
     {
@@ -137,6 +141,8 @@ public function removePlugin($fqcn)
 
     /**
      * Clears used headers.
+     *
+     * @return void
      */
     public function clearHeaders()
     {
@@ -148,6 +154,8 @@ public function clearHeaders()
 
     /**
      * @param array $headers
+     *
+     * @return void
      */
     public function addHeaders(array $headers)
     {
@@ -160,6 +168,8 @@ public function addHeaders(array $headers)
     /**
      * @param string $header
      * @param string $headerValue
+     *
+     * @return void
      */
     public function addHeaderValue($header, $headerValue)
     {
@@ -178,6 +188,8 @@ public function addHeaderValue($header, $headerValue)
      *
      * @param CacheItemPoolInterface $cachePool
      * @param array                  $config
+     *
+     * @return void
      */
     public function addCache(CacheItemPoolInterface $cachePool, array $config = [])
     {
@@ -190,6 +202,8 @@ public function addCache(CacheItemPoolInterface $cachePool, array $config = [])
 
     /**
      * Remove the cache plugin.
+     *
+     * @return void
      */
     public function removeCache()
     {
diff --git a/lib/Github/HttpClient/Message/ResponseMediator.php b/lib/Github/HttpClient/Message/ResponseMediator.php
index dcab5b4a979..67cc7016c54 100644
--- a/lib/Github/HttpClient/Message/ResponseMediator.php
+++ b/lib/Github/HttpClient/Message/ResponseMediator.php
@@ -56,13 +56,19 @@ public static function getPagination(ResponseInterface $response)
      */
     public static function getApiLimit(ResponseInterface $response)
     {
-        $remainingCalls = self::getHeader($response, 'X-RateLimit-Remaining');
+        $remainingCallsHeader = self::getHeader($response, 'X-RateLimit-Remaining');
 
-        if (null !== $remainingCalls && 1 > $remainingCalls) {
+        if (null === $remainingCallsHeader) {
+            return null;
+        }
+
+        $remainingCalls = (int) $remainingCallsHeader;
+
+        if (1 > $remainingCalls) {
             throw new ApiLimitExceedException($remainingCalls);
         }
 
-        return $remainingCalls;
+        return $remainingCallsHeader;
     }
 
     /**
diff --git a/lib/Github/HttpClient/Plugin/Authentication.php b/lib/Github/HttpClient/Plugin/Authentication.php
index de6237bef8b..a70593b8791 100644
--- a/lib/Github/HttpClient/Plugin/Authentication.php
+++ b/lib/Github/HttpClient/Plugin/Authentication.php
@@ -5,6 +5,7 @@
 use Github\Client;
 use Github\Exception\RuntimeException;
 use Http\Client\Common\Plugin;
+use Http\Promise\Promise;
 use Psr\Http\Message\RequestInterface;
 
 /**
@@ -16,10 +17,18 @@ class Authentication implements Plugin
 {
     use Plugin\VersionBridgePlugin;
 
+    /** @var string */
     private $tokenOrLogin;
+    /** @var string|null */
     private $password;
+    /** @var string|null */
     private $method;
 
+    /**
+     * @param string      $tokenOrLogin
+     * @param string|null $password
+     * @param string|null $method
+     */
     public function __construct($tokenOrLogin, $password, $method)
     {
         $this->tokenOrLogin = $tokenOrLogin;
@@ -28,7 +37,7 @@ public function __construct($tokenOrLogin, $password, $method)
     }
 
     /**
-     * {@inheritdoc}
+     * @return Promise
      */
     public function doHandleRequest(RequestInterface $request, callable $next, callable $first)
     {
diff --git a/lib/Github/HttpClient/Plugin/GithubExceptionThrower.php b/lib/Github/HttpClient/Plugin/GithubExceptionThrower.php
index dde0b45ccff..60382074a40 100644
--- a/lib/Github/HttpClient/Plugin/GithubExceptionThrower.php
+++ b/lib/Github/HttpClient/Plugin/GithubExceptionThrower.php
@@ -9,6 +9,7 @@
 use Github\Exception\ValidationFailedException;
 use Github\HttpClient\Message\ResponseMediator;
 use Http\Client\Common\Plugin;
+use Http\Promise\Promise;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
 
@@ -21,7 +22,7 @@ class GithubExceptionThrower implements Plugin
     use Plugin\VersionBridgePlugin;
 
     /**
-     * {@inheritdoc}
+     * @return Promise
      */
     public function doHandleRequest(RequestInterface $request, callable $next, callable $first)
     {
@@ -33,8 +34,8 @@ public function doHandleRequest(RequestInterface $request, callable $next, calla
             // If error:
             $remaining = ResponseMediator::getHeader($response, 'X-RateLimit-Remaining');
             if (null !== $remaining && 1 > $remaining && 'rate_limit' !== substr($request->getRequestTarget(), 1, 10)) {
-                $limit = ResponseMediator::getHeader($response, 'X-RateLimit-Limit');
-                $reset = ResponseMediator::getHeader($response, 'X-RateLimit-Reset');
+                $limit = (int) ResponseMediator::getHeader($response, 'X-RateLimit-Limit');
+                $reset = (int) ResponseMediator::getHeader($response, 'X-RateLimit-Reset');
 
                 throw new ApiLimitExceedException($limit, $reset);
             }
diff --git a/lib/Github/HttpClient/Plugin/History.php b/lib/Github/HttpClient/Plugin/History.php
index 0f59bbb65f9..c23621b87ed 100644
--- a/lib/Github/HttpClient/Plugin/History.php
+++ b/lib/Github/HttpClient/Plugin/History.php
@@ -28,6 +28,9 @@ public function getLastResponse()
         return $this->lastResponse;
     }
 
+    /**
+     * @return void
+     */
     public function addSuccess(RequestInterface $request, ResponseInterface $response)
     {
         $this->lastResponse = $response;
diff --git a/lib/Github/HttpClient/Plugin/HistoryTrait.php b/lib/Github/HttpClient/Plugin/HistoryTrait.php
index fbc5335d318..611db512917 100644
--- a/lib/Github/HttpClient/Plugin/HistoryTrait.php
+++ b/lib/Github/HttpClient/Plugin/HistoryTrait.php
@@ -15,6 +15,9 @@
      */
     trait HistoryTrait
     {
+        /**
+         * @return void
+         */
         public function addFailure(RequestInterface $request, ClientExceptionInterface $exception)
         {
         }
@@ -25,6 +28,9 @@ public function addFailure(RequestInterface $request, ClientExceptionInterface $
      */
     trait HistoryTrait
     {
+        /**
+         * @return void
+         */
         public function addFailure(RequestInterface $request, Exception $exception)
         {
         }
diff --git a/lib/Github/HttpClient/Plugin/PathPrepend.php b/lib/Github/HttpClient/Plugin/PathPrepend.php
index 1245c6923a2..3c55f72f13c 100644
--- a/lib/Github/HttpClient/Plugin/PathPrepend.php
+++ b/lib/Github/HttpClient/Plugin/PathPrepend.php
@@ -3,6 +3,7 @@
 namespace Github\HttpClient\Plugin;
 
 use Http\Client\Common\Plugin;
+use Http\Promise\Promise;
 use Psr\Http\Message\RequestInterface;
 
 /**
@@ -14,6 +15,7 @@ class PathPrepend implements Plugin
 {
     use Plugin\VersionBridgePlugin;
 
+    /** @var string */
     private $path;
 
     /**
@@ -25,7 +27,11 @@ public function __construct($path)
     }
 
     /**
-     * {@inheritdoc}
+     * @param RequestInterface $request
+     * @param callable         $next
+     * @param callable         $first
+     *
+     * @return Promise
      */
     public function doHandleRequest(RequestInterface $request, callable $next, callable $first)
     {
diff --git a/lib/Github/ResultPager.php b/lib/Github/ResultPager.php
index 24f2a32f135..defcde23e6a 100644
--- a/lib/Github/ResultPager.php
+++ b/lib/Github/ResultPager.php
@@ -161,6 +161,8 @@ public function fetchLast()
 
     /**
      * @param string $key
+     *
+     * @return bool
      */
     protected function has($key)
     {
@@ -169,6 +171,8 @@ protected function has($key)
 
     /**
      * @param string $key
+     *
+     * @return array
      */
     protected function get($key)
     {
@@ -178,6 +182,8 @@ protected function get($key)
 
             return ResponseMediator::getContent($result);
         }
+
+        return [];
     }
 
     /**
diff --git a/lib/Github/ResultPagerInterface.php b/lib/Github/ResultPagerInterface.php
index c5add903648..80660247900 100644
--- a/lib/Github/ResultPagerInterface.php
+++ b/lib/Github/ResultPagerInterface.php
@@ -43,6 +43,8 @@ public function fetchAll(ApiInterface $api, $method, array $parameters = []);
 
     /**
      * Method that performs the actual work to refresh the pagination property.
+     *
+     * @return void
      */
     public function postFetch();
 
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 1c57e1fef7e..9e84171f2c5 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -1,4 +1,15 @@
 parameters:
-    level: 4
+    checkMissingIterableValueType: false
+
+    level: 6
     paths:
         - lib
+
+    ignoreErrors:
+        # Ignore typehint errors on api classes
+        -
+            message: '#Method (.*) with no typehint specified\.#'
+            path: lib/Github/Api
+        -
+            message: '#Method (.*) has no return typehint specified\.#'
+            path: lib/Github/Api