diff --git a/km3io/utils/extract-dom-rates.py b/km3io/utils/extract-dom-rates.py
index 131d30ddb1a0010ac65a4a669bdd3853d7be9f8a..ee592b0371d855b5f654549ee94c133dc04f8461 100644
--- a/km3io/utils/extract-dom-rates.py
+++ b/km3io/utils/extract-dom-rates.py
@@ -35,7 +35,7 @@ def main():
 
     doms_rates = {}
     for dom in detector.dom_ids:
-        doms_rates[dom] = np.zeros(n_frames)
+        doms_rates[dom] = np.zeros(n_slices)
 
     for i in range (n_slices):
         rates = get_doms_rates(summary_slices, i)
@@ -47,7 +47,7 @@ def main():
     f.create_dataset("frame_indices",data=np.array(summary_slices.headers.frame_index))
     f.create_dataset("frame_times"  ,data=np.array(summary_slices.headers.UTC_seconds * 1e9 + summary_slices.headers.UTC_16nanosecondcycles * 16))
 
-    for key, value in dictionary.items():
+    for key, value in doms_rates.items():
         f.create_dataset(str(key), data=value)
 
 main()