diff --git a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/CleaningRuleMap.java b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/CleaningRuleMap.java
index 894d5d059..c650400af 100644
--- a/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/CleaningRuleMap.java
+++ b/dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/clean/CleaningRuleMap.java
@@ -3,13 +3,12 @@ package eu.dnetlib.dhp.oa.graph.clean;
 
 import java.io.Serializable;
 import java.util.HashMap;
+import java.util.concurrent.atomic.AtomicReference;
 
-import javax.jws.WebParam;
-
+import org.apache.commons.lang3.SerializationUtils;
 import org.apache.commons.lang3.StringUtils;
 
 import eu.dnetlib.dhp.common.FunctionalInterfaceSupport.SerializableConsumer;
-import eu.dnetlib.dhp.common.vocabulary.Vocabulary;
 import eu.dnetlib.dhp.common.vocabulary.VocabularyGroup;
 import eu.dnetlib.dhp.schema.common.ModelConstants;
 import eu.dnetlib.dhp.schema.oaf.*;
@@ -31,23 +30,30 @@ public class CleaningRuleMap extends HashMap<Class<?>, SerializableConsumer<Obje
 		return mapping;
 	}
 
-	private static void cleanSubject(VocabularyGroup vocabularies, Subject s) {
-		// TODO cleaning based on different subject vocabs can be added here
-		cleanSubjectForVocabulary(ModelConstants.DNET_SUBJECT_FOS_CLASSID, vocabularies, s);
+	private static void cleanSubject(VocabularyGroup vocabularies, Subject subject) {
+		if (cleanSubjectForVocabulary(ModelConstants.DNET_SUBJECT_FOS_CLASSID, vocabularies, subject)) {
+			return;
+		} else {
+			// TODO cleaning based on different subject vocabs can be added here
+		}
 	}
 
-	private static void cleanSubjectForVocabulary(String vocabularyId, VocabularyGroup vocabularies, Subject s) {
+	private static boolean cleanSubjectForVocabulary(String vocabularyId, VocabularyGroup vocabularies,
+		Subject subject) {
+		AtomicReference<Boolean> modified = new AtomicReference<>(false);
 		vocabularies.find(vocabularyId).ifPresent(vocabulary -> {
-			if (!ModelConstants.DNET_SUBJECT_KEYWORD.equalsIgnoreCase(s.getQualifier().getClassid())) {
+			if (!ModelConstants.DNET_SUBJECT_KEYWORD.equalsIgnoreCase(subject.getQualifier().getClassid())) {
 				return;
 			}
-			Qualifier newValue = vocabulary.lookup(s.getValue());
-			if (!s.getValue().equals(newValue.getClassid())) {
-				s.setValue(newValue.getClassid());
-				s.getQualifier().setClassid(vocabularyId);
-				s.getQualifier().setClassname(vocabulary.getName());
+			Qualifier newValue = vocabulary.lookup(subject.getValue());
+			if (!subject.getValue().equals(newValue.getClassid())) {
+				subject.setValue(newValue.getClassid());
+				subject.getQualifier().setClassid(vocabularyId);
+				subject.getQualifier().setClassname(vocabulary.getName());
+				modified.set(true);
 			}
 		});
+		return modified.get();
 	}
 
 	private static void cleanRelation(VocabularyGroup vocabularies, Relation r) {
diff --git a/dhp-workflows/dhp-graph-mapper/src/test/java/eu/dnetlib/dhp/oa/graph/clean/GraphCleaningFunctionsTest.java b/dhp-workflows/dhp-graph-mapper/src/test/java/eu/dnetlib/dhp/oa/graph/clean/GraphCleaningFunctionsTest.java
index f4c4581b1..0bfee1151 100644
--- a/dhp-workflows/dhp-graph-mapper/src/test/java/eu/dnetlib/dhp/oa/graph/clean/GraphCleaningFunctionsTest.java
+++ b/dhp-workflows/dhp-graph-mapper/src/test/java/eu/dnetlib/dhp/oa/graph/clean/GraphCleaningFunctionsTest.java
@@ -262,6 +262,20 @@ public class GraphCleaningFunctionsTest {
 		assertNotNull(fos_subjects);
 		assertEquals(2, fos_subjects.size());
 
+		assertTrue(
+			fos_subjects
+				.stream()
+				.anyMatch(
+					s -> "0101 mathematics".equals(s.getValue()) &
+						ModelConstants.DNET_SUBJECT_FOS_CLASSID.equals(s.getQualifier().getClassid())));
+
+		assertTrue(
+			fos_subjects
+				.stream()
+				.anyMatch(
+					s -> "0102 computer and information sciences".equals(s.getValue()) &
+						ModelConstants.DNET_SUBJECT_FOS_CLASSID.equals(s.getQualifier().getClassid())));
+
 		// TODO add more assertions to verity the cleaned values
 		System.out.println(MAPPER.writeValueAsString(p_cleaned));
 	}