diff --git a/CAL/CalibrationCommon/lib/datacontainers/holography_dataset.py b/CAL/CalibrationCommon/lib/datacontainers/holography_dataset.py
index b735177704169dfb4724a6f88e9d0d9f514929d2..a994ca19597cd3cc1cda0c84a51de7c660945658 100644
--- a/CAL/CalibrationCommon/lib/datacontainers/holography_dataset.py
+++ b/CAL/CalibrationCommon/lib/datacontainers/holography_dataset.py
@@ -217,7 +217,7 @@ class HolographyDataset():
         # frequency.
         central_beamlet = dict()
         for (frequency_string, beamlets) in pseudo_distance.items():
-            values = beamlets.values()
+            values = list(beamlets.values())
             keys = beamlets.keys()
             minimal_distance = min(values)
             # If I find a second beamlet that is 'closest' to the source for the