diff --git a/contrib/pyln-testing/pyln/testing/utils.py b/contrib/pyln-testing/pyln/testing/utils.py
index 5f5efa0287cd..947ff66dfe52 100644
--- a/contrib/pyln-testing/pyln/testing/utils.py
+++ b/contrib/pyln-testing/pyln/testing/utils.py
@@ -646,7 +646,7 @@ def __init__(
 
         if self.version >= Version.from_str('v23.11'):
             # Starting with v23.11 we ahve the `--developer` flag
-            self.early_opts = {'--developer': None}
+            self.early_opts = {'developer': None}
 
     def cleanup(self):
         # To force blackhole to exit, disconnect file must be truncated!