diff --git a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/CleaningFunctions.java b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/CleaningFunctions.java
index 84f88003b..12543d8c7 100644
--- a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/CleaningFunctions.java
+++ b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/CleaningFunctions.java
@@ -18,6 +18,7 @@ import eu.dnetlib.dhp.schema.oaf.*;
 public class CleaningFunctions {
 
 	public static final String ORCID_PREFIX_REGEX = "^http(s?):\\/\\/orcid\\.org\\/";
+	public static final String NONE = "none";
 
 	public static <T extends Oaf> T fixVocabularyNames(T value) {
 		if (value instanceof Datasource) {
@@ -106,6 +107,23 @@ public class CleaningFunctions {
 							.filter(sp -> StringUtils.isNotBlank(sp.getQualifier().getClassid()))
 							.collect(Collectors.toList()));
 			}
+			if (Objects.nonNull(r.getPid())) {
+				r
+						.setPid(
+								r
+										.getPid()
+										.stream()
+										.filter(Objects::nonNull)
+										.filter(sp -> StringUtils.isNotBlank(StringUtils.trim(sp.getValue())))
+										.filter(sp -> NONE.equalsIgnoreCase(sp.getValue()))
+										.filter(sp -> Objects.nonNull(sp.getQualifier()))
+										.filter(sp -> StringUtils.isNotBlank(sp.getQualifier().getClassid()))
+										.map(sp -> {
+											sp.setValue(StringUtils.trim(sp.getValue()));
+											return sp;
+										})
+										.collect(Collectors.toList()));
+			}
 			if (Objects.isNull(r.getResourcetype()) || StringUtils.isBlank(r.getResourcetype().getClassid())) {
 				r
 					.setResourcetype(