diff --git a/CHANGELOG.md b/CHANGELOG.md
index 660b78706..3cad9fe87 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,10 @@ You can find and compare releases at the [GitHub release page](https://github.co
 
 ## Unreleased
 
+### Changed
+
+- Respect settings in `GraphQL\Error\Warning` before calling custom `$warningHandler`
+
 ## v15.8.1
 
 ### Fixed
diff --git a/docs/class-reference.md b/docs/class-reference.md
index 5f0f11c4c..b90425118 100644
--- a/docs/class-reference.md
+++ b/docs/class-reference.md
@@ -1771,7 +1771,7 @@ const ALL = 63;
  *
  * @api
  */
-static function setWarningHandler(?callable $warningHandler = null): void
+static function setWarningHandler(?callable $warningHandler): void
 ```
 
 ```php
diff --git a/src/Error/Warning.php b/src/Error/Warning.php
index ac7a56028..850884dba 100644
--- a/src/Error/Warning.php
+++ b/src/Error/Warning.php
@@ -40,7 +40,7 @@ final class Warning
      *
      * @api
      */
-    public static function setWarningHandler(callable $warningHandler = null): void
+    public static function setWarningHandler(?callable $warningHandler): void
     {
         self::$warningHandler = $warningHandler;
     }
@@ -59,7 +59,7 @@ public static function setWarningHandler(callable $warningHandler = null): void
     public static function suppress($suppress = true): void
     {
         if ($suppress === true) {
-            self::$enableWarnings = 0;
+            self::$enableWarnings = self::NONE;
         } elseif ($suppress === false) {
             self::$enableWarnings = self::ALL;
             // @phpstan-ignore-next-line necessary until we can use proper unions
@@ -87,7 +87,7 @@ public static function enable($enable = true): void
         if ($enable === true) {
             self::$enableWarnings = self::ALL;
         } elseif ($enable === false) {
-            self::$enableWarnings = 0;
+            self::$enableWarnings = self::NONE;
             // @phpstan-ignore-next-line necessary until we can use proper unions
         } elseif (\is_int($enable)) {
             self::$enableWarnings |= $enable;
@@ -97,26 +97,31 @@ public static function enable($enable = true): void
         }
     }
 
-    public static function warnOnce(string $errorMessage, int $warningId, int $messageLevel = null): void
+    public static function warnOnce(string $errorMessage, int $warningId, int $messageLevel = \E_USER_WARNING): void
     {
-        $messageLevel ??= \E_USER_WARNING;
-
-        if (self::$warningHandler !== null) {
-            (self::$warningHandler)($errorMessage, $warningId, $messageLevel);
-        } elseif ((self::$enableWarnings & $warningId) > 0 && ! isset(self::$warned[$warningId])) {
-            self::$warned[$warningId] = true;
-            \trigger_error($errorMessage, $messageLevel);
+        if (isset(self::$warned[$warningId])) {
+            return;
         }
+
+        self::warn($errorMessage, $warningId, $messageLevel);
     }
 
-    public static function warn(string $errorMessage, int $warningId, int $messageLevel = null): void
+    public static function warn(string $errorMessage, int $warningId, int $messageLevel = \E_USER_WARNING): void
     {
-        $messageLevel ??= \E_USER_WARNING;
+        if (! self::shouldWarn($warningId)) {
+            return;
+        }
+        self::$warned[$warningId] = true;
 
-        if (self::$warningHandler !== null) {
+        if (isset(self::$warningHandler)) {
             (self::$warningHandler)($errorMessage, $warningId, $messageLevel);
-        } elseif ((self::$enableWarnings & $warningId) > 0) {
+        } else {
             \trigger_error($errorMessage, $messageLevel);
         }
     }
+
+    private static function shouldWarn(int $warningId): bool
+    {
+        return (self::$enableWarnings & $warningId) > 0;
+    }
 }
diff --git a/tests/Executor/ExecutorLazySchemaTest.php b/tests/Executor/ExecutorLazySchemaTest.php
index c40339fe6..3a2161fcb 100644
--- a/tests/Executor/ExecutorLazySchemaTest.php
+++ b/tests/Executor/ExecutorLazySchemaTest.php
@@ -129,16 +129,18 @@ public function testWarnsAboutSlowIsTypeOfForLazySchema(): void
         $result = Executor::execute($schema, Parser::parse($query));
         self::assertEquals($expected, $result);
 
+        $warnings = [];
+        Warning::setWarningHandler(function ($warning) use (&$warnings): void {
+            $warnings[] = $warning;
+        });
         Warning::enable(Warning::WARNING_FULL_SCHEMA_SCAN);
         $result = Executor::execute($schema, Parser::parse($query));
         self::markTestIncomplete('No longer works with PHPUnit 10, reintroduce with https://github.com/webonyx/graphql-php/pull/1393');
-        self::assertCount(1, $result->errors);
-        $error = $result->errors[0] ?? null;
-        self::assertInstanceOf(Error::class, $error);
-        self::assertSame(
+        self::assertEquals($expected, $result);
+
+        self::assertSame([
             'GraphQL Interface Type `Pet` returned `null` from its `resolveType` function for value: instance of GraphQL\Tests\Executor\TestClasses\Dog. Switching to slow resolution method using `isTypeOf` of all possible implementations. It requires full schema scan and degrades query performance significantly. Make sure your `resolveType` function always returns a valid implementation or throws.',
-            $error->getMessage()
-        );
+        ], $warnings);
     }
 
     public function testHintsOnConflictingTypeInstancesInDefinitions(): void