diff --git a/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/dto/api/v1/SimpleImageDataConfig.java b/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/dto/api/v1/SimpleImageDataConfig.java
index 5d9b274d0aa2d350fd06c0f0ef541476df2cf245..393a1c4fb2a69cc9cb8b1ea7fe66d6ee274ff2d4 100644
--- a/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/dto/api/v1/SimpleImageDataConfig.java
+++ b/screening/source/java/ch/systemsx/cisd/openbis/dss/etl/dto/api/v1/SimpleImageDataConfig.java
@@ -362,10 +362,8 @@ abstract public class SimpleImageDataConfig
 
     public void setGenerateThumbnailsPyramid(double[] zoomLevels)
     {
-        if (zoomLevels == null)
-        {
-            thumbnailsPyramid.clear();
-        } else
+        thumbnailsPyramid.clear();
+        if (zoomLevels != null)
         {
             for (double zoomLevel : zoomLevels)
             {