diff --git a/src/StateConfigValidator.php b/src/StateConfigValidator.php
index a7d6f4a..91fdb3f 100644
--- a/src/StateConfigValidator.php
+++ b/src/StateConfigValidator.php
@@ -309,7 +309,7 @@ private static function validateTransitionBehaviors(
         foreach ($behaviors as $behavior => $label) {
             if (isset($transitionConfig[$behavior])) {
                 try {
-                    $transitionConfig[$behavior] = self::normalizeArrayOrString($transitionConfig[$behavior]);
+                    $transitionConfig[$behavior] = self::normalizeArrayOrString(value: $transitionConfig[$behavior]);
                 } catch (InvalidArgumentException) {
                     throw new InvalidArgumentException(
                         message: "State '{$path}' has invalid {$behavior} configuration for event '{$eventName}'. ".
diff --git a/tests/StateConfigValidatorTest.php b/tests/StateConfigValidatorTest.php
index 082a24d..6ac52c4 100644
--- a/tests/StateConfigValidatorTest.php
+++ b/tests/StateConfigValidatorTest.php
@@ -117,6 +117,27 @@
         exceptionMessage: "State 'state_a' has invalid condition in transition for event 'EVENT'. Each condition must be an array with target/guards/actions."
     );
 });
+
+test('validates guards configuration in transitions', function (): void {
+    expect(fn () => MachineDefinition::define([
+        'id'      => 'machine',
+        'initial' => 'state_a',
+        'states'  => [
+            'state_a' => [
+                'on' => [
+                    'EVENT' => [
+                        'target' => 'state_b',
+                        'guards' => true, // Guards should be an array or a string
+                    ],
+                ],
+            ],
+        ],
+    ]))->toThrow(
+        InvalidArgumentException::class,
+        "State 'state_a' has invalid guards configuration for event 'EVENT'. Guards must be an array or string."
+    );
+});
+
 test('validates actions configuration in transitions', function (): void {
     expect(fn () => MachineDefinition::define([
         'id'      => 'machine',