diff --git a/Classes/DataProviding/Traits/Assert.php b/Classes/DataProviding/Traits/Assert.php
index 68af641..8ad37ee 100644
--- a/Classes/DataProviding/Traits/Assert.php
+++ b/Classes/DataProviding/Traits/Assert.php
@@ -10,6 +10,9 @@
  */
 trait Assert
 {
+    /**
+     * @phpstan-assert true $condition
+     */
     protected function assert(bool $condition, string $message): void
     {
         if ($condition) {