diff --git a/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/dto/api/impl/ImageDataSetInformation.java b/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/dto/api/impl/ImageDataSetInformation.java
index 02ede10eda74821aabfefbf6d4447572e9bf0596..26514bce22ade9d2f97433585640063e31605989 100644
--- a/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/dto/api/impl/ImageDataSetInformation.java
+++ b/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/dto/api/impl/ImageDataSetInformation.java
@@ -104,7 +104,7 @@ public class ImageDataSetInformation extends BasicDataSetInformation
     public String toString()
     {
         final StringBuilder buffer = new StringBuilder(super.toString());
-        appendNameAndObject(buffer, "images structure", imageDataSetStructure.toString());
+        appendNameAndObject(buffer, "images structure", imageDataSetStructure);
         appendNameAndObject(buffer, "container dataset", containerDatasetPermId);
         appendNameAndObject(buffer, "original dataset", this.getDataSetCode());
         if (this.tryGetThumbnailFilePaths() != null)