diff --git a/src/lighteval/metrics/sample_preparator.py b/src/lighteval/metrics/sample_preparator.py
index ad709033a..dc32d95c0 100644
--- a/src/lighteval/metrics/sample_preparator.py
+++ b/src/lighteval/metrics/sample_preparator.py
@@ -55,6 +55,7 @@ class PerplexityCorpusMetricInput(CorpusMetricInput):
 
 
 class GenerativePreparator:
+    @staticmethod
     def prepare(golds: list[str], predictions: list[str], **kwargs):
         """Prepares an individual generative example to the format expected by metrics computed at the corpus level (aggregated).