diff --git a/weboob/tools/capabilities/bank/transactions.py b/weboob/tools/capabilities/bank/transactions.py
index a4b4f8dd..147dfcf4 100644
--- a/weboob/tools/capabilities/bank/transactions.py
+++ b/weboob/tools/capabilities/bank/transactions.py
@@ -35,7 +35,8 @@ class FrenchTransaction(Transaction):
     """
     PATTERNS = []
 
-    def clean_amount(self, text):
+    @classmethod
+    def clean_amount(klass, text):
         """
         Clean a string containing an amount.
         """