diff --git a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/cfhb/CleanCfHbSparkJob.java b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/cfhb/CleanCfHbSparkJob.java
index 7cc26745b..531b415ed 100644
--- a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/cfhb/CleanCfHbSparkJob.java
+++ b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/cfhb/CleanCfHbSparkJob.java
@@ -151,11 +151,32 @@ public class CleanCfHbSparkJob {
 	private static <T extends Result> FlatMapFunction<T, IdCfHbMapping> flattenCfHbFn() {
 		return r -> Stream
 			.concat(
-				r.getCollectedfrom().stream().map(KeyValue::getKey),
+				Optional
+					.ofNullable(r.getCollectedfrom())
+					.map(cf -> cf.stream().map(KeyValue::getKey))
+					.orElse(Stream.empty()),
 				Stream
 					.concat(
-						r.getInstance().stream().map(Instance::getHostedby).map(KeyValue::getKey),
-						r.getInstance().stream().map(Instance::getCollectedfrom).map(KeyValue::getKey)))
+						Optional
+							.ofNullable(r.getInstance())
+							.map(
+								instances -> instances
+									.stream()
+									.map(i -> Optional.ofNullable(i.getHostedby()).map(KeyValue::getKey).orElse("")))
+							.orElse(Stream.empty())
+							.filter(StringUtils::isNotBlank),
+						Optional
+							.ofNullable(r.getInstance())
+							.map(
+								instances -> instances
+									.stream()
+									.map(
+										i -> Optional
+											.ofNullable(i.getCollectedfrom())
+											.map(KeyValue::getKey)
+											.orElse("")))
+							.orElse(Stream.empty())
+							.filter(StringUtils::isNotBlank)))
 			.distinct()
 			.filter(StringUtils::isNotBlank)
 			.map(cfHb -> asIdCfHbMapping(r.getId(), cfHb))