diff --git a/src/km3io/tools.py b/src/km3io/tools.py
index 1c92e471febd6b9acbfbab577f69fc6afb318616..ae6b015fe0c7da409c8f84d776dab02b241af522 100644
--- a/src/km3io/tools.py
+++ b/src/km3io/tools.py
@@ -539,7 +539,7 @@ def is_3dmuon(trigger_mask):
     return is_bit_set(trigger_mask, ktrg.JTRIGGER3DMUON)
 
 
-def get_w2defs_idx(f):
+def get_w2list_idx(f):
     """
     Get the correct w2list_idx for the given file, or None if there is none.