diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4f799e49..8c01934e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 ### Fixed
 - ensure numeric issues in const are correctly evaluated ([#805](https://github.com/jsonrainbow/json-schema/pull/805))
+- fix 6.3.0 regression with comparison of null values during validation ([#806](https://github.com/jsonrainbow/json-schema/issues/806))
 
 ## [6.3.0] - 2025-03-14
 ### Fixed
diff --git a/src/JsonSchema/Tool/DeepComparer.php b/src/JsonSchema/Tool/DeepComparer.php
index 70b16ef0..fb99b141 100644
--- a/src/JsonSchema/Tool/DeepComparer.php
+++ b/src/JsonSchema/Tool/DeepComparer.php
@@ -12,6 +12,10 @@ class DeepComparer
      */
     public static function isEqual($left, $right): bool
     {
+        if ($left === null && $right === null) {
+            return true;
+        }
+
         $isLeftScalar = is_scalar($left);
         $isRightScalar = is_scalar($right);
 
diff --git a/tests/Tool/DeepComparerTest.php b/tests/Tool/DeepComparerTest.php
index 112ace66..cb7b02aa 100644
--- a/tests/Tool/DeepComparerTest.php
+++ b/tests/Tool/DeepComparerTest.php
@@ -27,6 +27,7 @@ public function testComparesDeepEqualForNotEqualLeftAndRight($left, $right): voi
 
     public function equalDataProvider(): \Generator
     {
+        yield 'Null null' => [null, null];
         yield 'Boolean true' => [true, true];
         yield 'Boolean false' => [false, false];
 
@@ -49,6 +50,7 @@ public function equalDataProvider(): \Generator
 
     public function notEqualDataProvider(): \Generator
     {
+        yield 'Null true' => [null, true];
         yield 'Boolean true/false' => [true, false];
 
         yield 'Integer one/two' => [1, 2];