diff --git a/src/lib/Form/DataTransformer/DateTimePickerTransformer.php b/src/lib/Form/DataTransformer/DateTimePickerTransformer.php
index cbe49493c4..436ca1e410 100644
--- a/src/lib/Form/DataTransformer/DateTimePickerTransformer.php
+++ b/src/lib/Form/DataTransformer/DateTimePickerTransformer.php
@@ -32,7 +32,7 @@ public function transform($value)
 
         if (!$value instanceof DateTimeInterface) {
             throw new TransformationFailedException(
-                sprintf('Found %s instead of %s', gettype($value), DateTimeInterface::class)
+                sprintf('Found %s instead of %s', get_debug_type($value), DateTimeInterface::class)
             );
         }