diff --git a/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/metadata/MetaDataFieldSkeleton.java b/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/metadata/MetaDataFieldSkeleton.java
index 4bc1d73..68b0eab 100644
--- a/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/metadata/MetaDataFieldSkeleton.java
+++ b/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/metadata/MetaDataFieldSkeleton.java
@@ -467,6 +467,9 @@ public class MetaDataFieldSkeleton extends Composite{
 			else{
 
 				List<String> listboxValues = getFieldCurrentValue();
+				
+				if(listboxValues.isEmpty() && field.getMandatory())
+					return MANDATORY_ATTRIBUTE_MISSING;
 
 				for (String value : listboxValues) {
 					if(!field.getMandatory()){