diff --git a/fiona/__init__.py b/fiona/__init__.py
index 9556ec99..0ba28c1e 100644
--- a/fiona/__init__.py
+++ b/fiona/__init__.py
@@ -300,7 +300,7 @@ def func(*args, **kwds):
 
         try:
             if opener:
-                log.debug("Registering opener: raw_dataset_path=%r, opener=%r", raw_dataset_path, mode, opener)
+                log.debug("Registering opener: raw_dataset_path=%r, opener=%r", raw_dataset_path, opener)
                 vsi_path_ctx = _opener_registration(raw_dataset_path, opener)
                 registered_vsi_path = stack.enter_context(vsi_path_ctx)
                 log.debug("Registered vsi path: registered_vsi_path%r", registered_vsi_path)