diff --git a/src/Symfony/Component/ErrorHandler/Exception/FlattenException.php b/src/Symfony/Component/ErrorHandler/Exception/FlattenException.php
index 37d95861414bf..c5c88d28046e4 100644
--- a/src/Symfony/Component/ErrorHandler/Exception/FlattenException.php
+++ b/src/Symfony/Component/ErrorHandler/Exception/FlattenException.php
@@ -275,19 +275,22 @@ public function setTraceFromThrowable(\Throwable $throwable): self
     /**
      * @return $this
      */
-    public function setTrace($trace, $file, $line): self
+    public function setTrace($trace, $file = null, $line = null): self
     {
         $this->trace = [];
-        $this->trace[] = [
-            'namespace' => '',
-            'short_class' => '',
-            'class' => '',
-            'type' => '',
-            'function' => '',
-            'file' => $file,
-            'line' => $line,
-            'args' => [],
-        ];
+        if (null !== $file) {
+            $this->trace[] = [
+                'namespace' => '',
+                'short_class' => '',
+                'class' => '',
+                'type' => '',
+                'function' => '',
+                'file' => $file,
+                'line' => $line,
+                'args' => [],
+            ];
+        }
+
         foreach ($trace as $entry) {
             $class = '';
             $namespace = '';
@@ -357,6 +360,18 @@ private function getClassNameFromIncomplete(\__PHP_Incomplete_Class $value): str
 
     public function getTraceAsString(): string
     {
+        if (null === $this->traceAsString) {
+            $this->traceAsString = '';
+            if (null !== $this->trace) {
+                foreach ($this->trace as $i => $trace) {
+                    if (0 === $i) {
+                        continue;
+                    }
+                    $this->traceAsString .= sprintf('#%d %s(%s): %s%s%s()', $i - 1, $trace['file'], $trace['line'], $trace['class'], $trace['type'], $trace['function']).\PHP_EOL;
+                }
+            }
+        }
+
         return $this->traceAsString;
     }
 
diff --git a/src/Symfony/Component/ErrorHandler/Tests/Exception/FlattenExceptionTest.php b/src/Symfony/Component/ErrorHandler/Tests/Exception/FlattenExceptionTest.php
index 30c5234669adf..fad4ad3808ee0 100644
--- a/src/Symfony/Component/ErrorHandler/Tests/Exception/FlattenExceptionTest.php
+++ b/src/Symfony/Component/ErrorHandler/Tests/Exception/FlattenExceptionTest.php
@@ -29,6 +29,10 @@
 use Symfony\Component\HttpKernel\Exception\TooManyRequestsHttpException;
 use Symfony\Component\HttpKernel\Exception\UnauthorizedHttpException;
 use Symfony\Component\HttpKernel\Exception\UnsupportedMediaTypeHttpException;
+use Symfony\Component\Serializer\Encoder\JsonEncoder;
+use Symfony\Component\Serializer\Normalizer\ArrayDenormalizer;
+use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
+use Symfony\Component\Serializer\Serializer;
 
 class FlattenExceptionTest extends TestCase
 {
@@ -405,6 +409,22 @@ public function testToStringParent()
         $this->assertSame($exception->__toString(), $flattened->getAsString());
     }
 
+    public function testSerialize()
+    {
+        $serializer = new Serializer([new ArrayDenormalizer(), new ObjectNormalizer()], [new JsonEncoder()]);
+
+        $flattened = FlattenException::createFromThrowable(new \LogicException('Bad things happened'));
+        $trace = $flattened->getTraceAsString();
+        $data = $serializer->serialize($flattened, 'json');
+
+        $restored = $serializer->deserialize($data, FlattenException::class, 'json');
+        $restoredTrace = $restored->getTraceAsString();
+
+        // Verify that they look kind of similar.
+        $this->assertEquals(substr($trace, 0, 100), substr($restoredTrace, 0, 100));
+        $this->assertEquals(\count(explode(\PHP_EOL, $trace)), \count(explode(\PHP_EOL, $restoredTrace)));
+    }
+
     private function createException($foo): \Exception
     {
         return new \Exception();
diff --git a/src/Symfony/Component/PropertyAccess/PropertyAccessor.php b/src/Symfony/Component/PropertyAccess/PropertyAccessor.php
index d3f046a074ce4..12b1e2f38e7a3 100644
--- a/src/Symfony/Component/PropertyAccess/PropertyAccessor.php
+++ b/src/Symfony/Component/PropertyAccess/PropertyAccessor.php
@@ -610,6 +610,7 @@ private function getWriteInfo(string $class, string $property, $value): Property
             'enable_magic_methods_extraction' => $this->magicMethodsFlags,
             'enable_constructor_extraction' => false,
             'enable_adder_remover_extraction' => $useAdderAndRemover,
+            'value' => $value,
         ]);
 
         if (isset($item)) {
diff --git a/src/Symfony/Component/PropertyInfo/Extractor/ReflectionExtractor.php b/src/Symfony/Component/PropertyInfo/Extractor/ReflectionExtractor.php
index 5287979945af3..df1058a2e7d08 100644
--- a/src/Symfony/Component/PropertyInfo/Extractor/ReflectionExtractor.php
+++ b/src/Symfony/Component/PropertyInfo/Extractor/ReflectionExtractor.php
@@ -388,6 +388,12 @@ public function getWriteInfo(string $class, string $property, array $context = [
             }
 
             $method = $reflClass->getMethod($methodName);
+            /** @var \ReflectionParameter $parameter */
+            $parameter = $method->getParameters()[0];
+            if (\array_key_exists('value', $context) && null === $context['value'] && !$parameter->allowsNull()) {
+                $errors[] = sprintf('The method "%s" in class "%s" was found but does not allow null.', $methodName, $class);
+                continue;
+            }
 
             if (!\in_array($mutatorPrefix, $this->arrayMutatorPrefixes, true)) {
                 return new PropertyWriteInfo(PropertyWriteInfo::TYPE_METHOD, $methodName, $this->getWriteVisiblityForMethod($method), $method->isStatic());