diff --git a/dhp-workflows/dhp-aggregation/src/main/java/eu/dnetlib/dhp/collection/plugin/osf/OsfPreprintsIterator.java b/dhp-workflows/dhp-aggregation/src/main/java/eu/dnetlib/dhp/collection/plugin/osf/OsfPreprintsIterator.java
index 9484297d0..292e1c322 100644
--- a/dhp-workflows/dhp-aggregation/src/main/java/eu/dnetlib/dhp/collection/plugin/osf/OsfPreprintsIterator.java
+++ b/dhp-workflows/dhp-aggregation/src/main/java/eu/dnetlib/dhp/collection/plugin/osf/OsfPreprintsIterator.java
@@ -5,6 +5,7 @@ import java.util.Iterator;
 import java.util.Queue;
 import java.util.concurrent.PriorityBlockingQueue;
 
+import org.apache.commons.lang3.StringUtils;
 import org.dom4j.Document;
 import org.dom4j.DocumentHelper;
 import org.dom4j.Element;
@@ -46,13 +47,14 @@ public class OsfPreprintsIterator implements Iterator<String> {
 
 	private void initQueue() {
 		this.currentUrl = this.baseUrl + "?filter:is_published:d=true&format=json&page[size]=" + this.pageSize;
+
 		log.info("REST calls starting with {}", this.currentUrl);
 	}
 
 	@Override
 	public boolean hasNext() {
 		synchronized (this.recordQueue) {
-			while (this.recordQueue.isEmpty() && !this.currentUrl.isEmpty()) {
+			while (this.recordQueue.isEmpty() && StringUtils.isNotBlank(this.currentUrl) && this.currentUrl.startsWith("http")) {
 				try {
 					this.currentUrl = downloadPage(this.currentUrl);
 				} catch (final CollectorException e) {
@@ -88,12 +90,18 @@ public class OsfPreprintsIterator implements Iterator<String> {
 			group.addElement("preprint").add(n);
 
 			for (final Object o1 : n.selectNodes(".//contributors//href")) {
-				final Document doc1 = downloadUrl(((Node) o1).getText(), 0);
-				group.addElement("contributors").add(doc1.getRootElement().detach());
+				final String href = ((Node) o1).getText();
+				if (StringUtils.isNotBlank(href) && href.startsWith("http")) {
+					final Document doc1 = downloadUrl(href, 0);
+					group.addElement("contributors").add(doc1.getRootElement().detach());
+				}
 			}
 			for (final Object o1 : n.selectNodes(".//primary_file//href")) {
-				final Document doc1 = downloadUrl(((Node) o1).getText(), 0);
-				group.addElement("primary_file").add(doc1.getRootElement().detach());
+				final String href = ((Node) o1).getText();
+				if (StringUtils.isNotBlank(href) && href.startsWith("http")) {
+					final Document doc1 = downloadUrl(href, 0);
+					group.addElement("primary_file").add(doc1.getRootElement().detach());
+				}
 			}
 
 			this.recordQueue.add(DocumentHelper.createDocument(group).asXML());
diff --git a/dhp-workflows/dhp-aggregation/src/test/java/eu/dnetlib/dhp/collection/plugin/osf/OsfPreprintsCollectorPluginTest.java b/dhp-workflows/dhp-aggregation/src/test/java/eu/dnetlib/dhp/collection/plugin/osf/OsfPreprintsCollectorPluginTest.java
index efba0c72e..fe2274c89 100644
--- a/dhp-workflows/dhp-aggregation/src/test/java/eu/dnetlib/dhp/collection/plugin/osf/OsfPreprintsCollectorPluginTest.java
+++ b/dhp-workflows/dhp-aggregation/src/test/java/eu/dnetlib/dhp/collection/plugin/osf/OsfPreprintsCollectorPluginTest.java
@@ -18,6 +18,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import eu.dnetlib.dhp.collection.ApiDescriptor;
+import eu.dnetlib.dhp.collection.plugin.utils.JsonUtils;
 import eu.dnetlib.dhp.common.aggregation.AggregatorReport;
 import eu.dnetlib.dhp.common.collection.CollectorException;
 import eu.dnetlib.dhp.common.collection.HttpClientParams;
@@ -110,4 +111,10 @@ public class OsfPreprintsCollectorPluginTest {
 
 	}
 
+	@Test
+	void testXML() {
+		final String xml = JsonUtils.convertToXML("{'next':null}");
+		System.out.println(xml);
+	}
+
 }