diff --git a/composer-dependency-analyser.php b/composer-dependency-analyser.php
index 730b35e..a7801ad 100644
--- a/composer-dependency-analyser.php
+++ b/composer-dependency-analyser.php
@@ -21,6 +21,9 @@
 if (version_compare(PHP_VERSION, '8.3.0', '>=')) {
     $config->ignoreErrorsOnPackage('symfony/polyfill-php83', [ErrorType::UNUSED_DEPENDENCY]);
 }
+if (version_compare(PHP_VERSION, '8.4.0', '>=')) {
+    $config->ignoreErrorsOnPackage('symfony/polyfill-php84', [ErrorType::UNUSED_DEPENDENCY]);
+}
 
 if (!class_exists(DataProvider::class)) {
     $config->ignoreUnknownClasses([DataProvider::class]);
diff --git a/composer.json b/composer.json
index f64fa16..d0d6bec 100644
--- a/composer.json
+++ b/composer.json
@@ -19,10 +19,10 @@
         "symfony/form": "^5.4 || ^6.0 || ^7.0",
         "symfony/http-kernel": "^5.4 || ^6.0 || ^7.0",
         "symfony/options-resolver": "^5.4 || ^6.0 || ^7.0",
-        "symfony/polyfill-php83": "^1.27",
+        "symfony/polyfill-php83": "^1.33",
+        "symfony/polyfill-php84": "^1.33",
         "symfony/property-info": "^5.4 || ^6.0 || ^7.0",
-        "symfony/validator": "^5.4 || ^6.0 || ^7.0",
-        "webmozart/assert": "^1.10"
+        "symfony/validator": "^5.4 || ^6.0 || ^7.0"
     },
     "require-dev": {
         "ergebnis/composer-normalize": "^2.42",
diff --git a/src/Form/DataTransformer/CronExpressionToPartsTransformer.php b/src/Form/DataTransformer/CronExpressionToPartsTransformer.php
index 8a0e4cd..9a87d29 100644
--- a/src/Form/DataTransformer/CronExpressionToPartsTransformer.php
+++ b/src/Form/DataTransformer/CronExpressionToPartsTransformer.php
@@ -7,7 +7,6 @@
 use Cron\CronExpression;
 use Symfony\Component\Form\DataTransformerInterface;
 use Symfony\Component\Form\Exception\TransformationFailedException;
-use Webmozart\Assert\Assert;
 
 /**
  * @template-implements DataTransformerInterface<CronExpression, array<string, array<string>>>
@@ -69,9 +68,7 @@ public function reverseTransform($value): CronExpression
             throw $exception;
         }
 
-        try {
-            Assert::allIsArray($value);
-        } catch (\InvalidArgumentException $e) {
+        if (!self::allArrayScalar($value)) {
             throw $exception;
         }
 
@@ -90,14 +87,23 @@ public function reverseTransform($value): CronExpression
         }
     }
 
+    /**
+     * @psalm-assert array<string, array<scalar>> $value
+     */
+    private static function allArrayScalar(array $value): bool
+    {
+        return array_all($value, fn (mixed $s) => is_array($s) && array_all($s, fn (mixed $o) => is_scalar($o)));
+    }
+
+    /**
+     * @param array<scalar> $cronArray
+     */
     private function convertCronParts(array $cronArray): string
     {
         if ([] === $cronArray) {
             return '*';
         }
 
-        Assert::allScalar($cronArray);
-
         return implode(',', $cronArray);
     }
 
diff --git a/src/Form/DataTransformer/CronExpressionToStringPartsTransformer.php b/src/Form/DataTransformer/CronExpressionToStringPartsTransformer.php
index 023c967..20605fe 100644
--- a/src/Form/DataTransformer/CronExpressionToStringPartsTransformer.php
+++ b/src/Form/DataTransformer/CronExpressionToStringPartsTransformer.php
@@ -7,7 +7,6 @@
 use Cron\CronExpression;
 use Symfony\Component\Form\DataTransformerInterface;
 use Symfony\Component\Form\Exception\TransformationFailedException;
-use Webmozart\Assert\Assert;
 
 /**
  * @template-implements DataTransformerInterface<CronExpression, array<string,string>>
@@ -69,9 +68,7 @@ public function reverseTransform($value): CronExpression
             throw $exception;
         }
 
-        try {
-            Assert::allString($value);
-        } catch (\InvalidArgumentException $e) {
+        if (!self::allString($value)) {
             throw $exception;
         }
 
@@ -89,4 +86,12 @@ public function reverseTransform($value): CronExpression
 
         return $cronExpression;
     }
+
+    /**
+     * @psalm-assert iterable<string> $value
+     */
+    private static function allString(array $value): bool
+    {
+        return array_all($value, fn (mixed $s) => is_string($s));
+    }
 }