diff --git a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/raw/AbstractMdRecordToOafMapper.java b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/raw/AbstractMdRecordToOafMapper.java
index cdc707084f..0a32766c98 100644
--- a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/raw/AbstractMdRecordToOafMapper.java
+++ b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/raw/AbstractMdRecordToOafMapper.java
@@ -143,7 +143,7 @@ public abstract class AbstractMdRecordToOafMapper {
 			return createOafs(doc, type, instances, collectedFrom, info, lastUpdateTimestamp);
 		} catch (DocumentException e) {
 			log.error("Error with record:\n" + xml);
-			return Lists.newArrayList();
+			return null;
 		}
 	}
 
diff --git a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/raw/GenerateEntitiesApplication.java b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/raw/GenerateEntitiesApplication.java
index e9de43f7fa..290a226565 100644
--- a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/raw/GenerateEntitiesApplication.java
+++ b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/raw/GenerateEntitiesApplication.java
@@ -126,8 +126,6 @@ public class GenerateEntitiesApplication {
 		log.info("Generate entities from files:");
 		existingSourcePaths.forEach(log::info);
 
-		JavaRDD<Oaf> inputRdd = sc.emptyRDD();
-
 		for (final String sp : existingSourcePaths) {
 			RDD<String> invalidRecords = sc
 				.sequenceFile(sp, Text.class, Text.class)
@@ -141,7 +139,11 @@ public class GenerateEntitiesApplication {
 				.mode(SaveMode.Append)
 				.option("compression", "gzip")
 				.text(invalidPath);
+		}
 
+		JavaRDD<Oaf> inputRdd = sc.emptyRDD();
+
+		for (final String sp : existingSourcePaths) {
 			inputRdd = inputRdd
 				.union(
 					sc
@@ -223,7 +225,7 @@ public class GenerateEntitiesApplication {
 		final boolean shouldHashId,
 		final VocabularyGroup vocs) {
 
-		if (convertToListOaf(id, s, shouldHashId, vocs).isEmpty()) {
+		if (Objects.isNull(convertToListOaf(id, s, shouldHashId, vocs))) {
 			return s;
 		}
 		return null;