diff --git a/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/Hdf5ThumbnailGenerator.java b/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/Hdf5ThumbnailGenerator.java
index 287130aabc5de0d095a924c46b21417131e12c86..66112b4e58c8997fcc2e7c5a18cd6c09747b8f53 100644
--- a/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/Hdf5ThumbnailGenerator.java
+++ b/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/Hdf5ThumbnailGenerator.java
@@ -105,7 +105,8 @@ class Hdf5ThumbnailGenerator implements IHdf5WriterClient
             }
         } catch (IOException ex)
         {
-            ex.printStackTrace();
+            operationLog
+                    .warn("Retriable error when creating thumbnail '" + thumbnailPath + "'", ex);
             return Status.createRetriableError(String.format(
                     "Could not generate a thumbnail '%s': %s", thumbnailPath, ex.getMessage()));
         }