diff --git a/src/main/java/org/gcube/dataharvest/harvester/sobigdata/SoBigDataHarvester.java b/src/main/java/org/gcube/dataharvest/harvester/sobigdata/SoBigDataHarvester.java
index 4a3baf9..63ce27e 100644
--- a/src/main/java/org/gcube/dataharvest/harvester/sobigdata/SoBigDataHarvester.java
+++ b/src/main/java/org/gcube/dataharvest/harvester/sobigdata/SoBigDataHarvester.java
@@ -94,8 +94,11 @@ public abstract class SoBigDataHarvester extends BasicHarvester {
 		
 		for(int i=1; i<contexts.getLength()-1; i++){
 			Node context = contexts.item(i);
-			String contextToExclude = context.getChildNodes().item(0).getNodeValue(); 
-			excludedContexts.add(contextToExclude);
+			NodeList nList = context.getChildNodes();
+			if(nList.item(0)!=null) {
+				String contextToExclude = nList.item(0).getNodeValue(); 
+				excludedContexts.add(contextToExclude);
+			}
 		}
 		
 		return excludedContexts;