diff --git a/km3io/utils/KModuleRates.py b/km3io/utils/KModuleRates.py
index 3c8e5ed8dc8cfff3fdbd4c563670f359b13070c6..b726c3e6c8386e4307f30bb0ae190794519185e4 100644
--- a/km3io/utils/KModuleRates.py
+++ b/km3io/utils/KModuleRates.py
@@ -71,7 +71,7 @@ def main():
 
     dom2index = {}
     index2dom = {}
-    for idx, dom in enumerate(detector.dom_ids):
+    for idx, dom in enumerate(dom_ids):
         dom2index[dom] = idx
         index2dom[idx] = dom