diff --git a/src/Error/Warning.php b/src/Error/Warning.php
index 9157b05..25828b1 100644
--- a/src/Error/Warning.php
+++ b/src/Error/Warning.php
@@ -4,6 +4,8 @@ declare(strict_types=1);
 
 namespace GraphQL\Error;
 
+use GraphQL\Exception\InvalidArgument;
+use function is_int;
 use function trigger_error;
 use const E_USER_WARNING;
 
@@ -15,12 +17,12 @@ use const E_USER_WARNING;
  */
 final class Warning
 {
-    const WARNING_ASSIGN             = 2;
-    const WARNING_CONFIG             = 4;
-    const WARNING_FULL_SCHEMA_SCAN   = 8;
-    const WARNING_CONFIG_DEPRECATION = 16;
-    const WARNING_NOT_A_TYPE         = 32;
-    const ALL                        = 63;
+    public const WARNING_ASSIGN             = 2;
+    public const WARNING_CONFIG             = 4;
+    public const WARNING_FULL_SCHEMA_SCAN   = 8;
+    public const WARNING_CONFIG_DEPRECATION = 16;
+    public const WARNING_NOT_A_TYPE         = 32;
+    public const ALL                        = 63;
 
     /** @var int */
     private static $enableWarnings = self::ALL;
@@ -37,7 +39,7 @@ final class Warning
      *
      * @api
      */
-    public static function setWarningHandler(?callable $warningHandler = null)
+    public static function setWarningHandler(?callable $warningHandler = null) : void
     {
         self::$warningHandler = $warningHandler;
     }
@@ -54,14 +56,16 @@ final class Warning
      *
      * @api
      */
-    public static function suppress($suppress = true)
+    public static function suppress($suppress = true) : void
     {
         if ($suppress === true) {
             self::$enableWarnings = 0;
         } elseif ($suppress === false) {
             self::$enableWarnings = self::ALL;
-        } else {
+        } elseif (is_int($suppress)) {
             self::$enableWarnings &= ~$suppress;
+        } else {
+            throw InvalidArgument::fromExpectedTypeAndArgument('bool|int', $suppress);
         }
     }
 
@@ -77,18 +81,20 @@ final class Warning
      *
      * @api
      */
-    public static function enable($enable = true)
+    public static function enable($enable = true) : void
     {
         if ($enable === true) {
             self::$enableWarnings = self::ALL;
         } elseif ($enable === false) {
             self::$enableWarnings = 0;
-        } else {
+        } elseif (is_int($enable)) {
             self::$enableWarnings |= $enable;
+        } else {
+            throw InvalidArgument::fromExpectedTypeAndArgument('bool|int', $enable);
         }
     }
 
-    public static function warnOnce($errorMessage, $warningId, $messageLevel = null)
+    public static function warnOnce(string $errorMessage, int $warningId, ?int $messageLevel = null) : void
     {
         if (self::$warningHandler) {
             $fn = self::$warningHandler;
@@ -99,7 +105,7 @@ final class Warning
         }
     }
 
-    public static function warn($errorMessage, $warningId, $messageLevel = null)
+    public static function warn(string $errorMessage, int $warningId, ?int $messageLevel = null) : void
     {
         if (self::$warningHandler) {
             $fn = self::$warningHandler;
diff --git a/src/Exception/InvalidArgument.php b/src/Exception/InvalidArgument.php
new file mode 100644
index 0000000..eea34d5
--- /dev/null
+++ b/src/Exception/InvalidArgument.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GraphQL\Exception;
+
+use InvalidArgumentException;
+use function gettype;
+use function sprintf;
+
+final class InvalidArgument extends InvalidArgumentException
+{
+    /**
+     * @param mixed $argument
+     */
+    public static function fromExpectedTypeAndArgument(string $expectedType, $argument) : self
+    {
+        return new self(sprintf('Expected type "%s", got "%s"', $expectedType, gettype($argument)));
+    }
+}
diff --git a/tests/Exception/InvalidArgumentTest.php b/tests/Exception/InvalidArgumentTest.php
new file mode 100644
index 0000000..381c5ee
--- /dev/null
+++ b/tests/Exception/InvalidArgumentTest.php
@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GraphQL\Tests\Exception;
+
+use GraphQL\Exception\InvalidArgument;
+use PHPUnit\Framework\TestCase;
+
+final class InvalidArgumentTest extends TestCase
+{
+    public function testFromExpectedTypeAndArgument() : void
+    {
+        $exception = InvalidArgument::fromExpectedTypeAndArgument('bool|int', 'stringValue');
+
+        self::assertSame('Expected type "bool|int", got "string"', $exception->getMessage());
+    }
+}