diff --git a/src/main/java/org/openehealth/app/xdstofhir/registry/common/mapper/AbstractXdsToFhirMapper.java b/src/main/java/org/openehealth/app/xdstofhir/registry/common/mapper/AbstractXdsToFhirMapper.java
index 5b0d6ff..479da17 100644
--- a/src/main/java/org/openehealth/app/xdstofhir/registry/common/mapper/AbstractXdsToFhirMapper.java
+++ b/src/main/java/org/openehealth/app/xdstofhir/registry/common/mapper/AbstractXdsToFhirMapper.java
@@ -77,7 +77,7 @@ protected Coding map(final Code code) {
     protected Reference fromAuthor(final Author author) {
         var role = new PractitionerRole();
         var doc = new Practitioner();
-        if(!author.getAuthorPerson().isEmpty()) {
+        if((author.getAuthorPerson() != null) && !author.getAuthorPerson().isEmpty()) {
             if (!author.getAuthorPerson().getName().isEmpty())
                 doc.setName(singletonList(fromName(author.getAuthorPerson().getName())));
             if (!author.getAuthorPerson().getId().isEmpty())
diff --git a/src/main/java/org/openehealth/app/xdstofhir/registry/query/StoredQueryMapper.java b/src/main/java/org/openehealth/app/xdstofhir/registry/query/StoredQueryMapper.java
index 4a0f549..6feaf15 100644
--- a/src/main/java/org/openehealth/app/xdstofhir/registry/query/StoredQueryMapper.java
+++ b/src/main/java/org/openehealth/app/xdstofhir/registry/query/StoredQueryMapper.java
@@ -117,7 +117,7 @@ public static void mapPatientIdToQuery(PatientIdBasedStoredQuery query, IQuery<B
         var patientId = query.getPatientId();
 
         var identifier = DocumentReference.PATIENT
-                .hasChainedProperty(Patient.IDENTIFIER.exactly().systemAndIdentifier(
+                .hasChainedProperty("Patient", Patient.IDENTIFIER.exactly().systemAndIdentifier(
                         OID_URN + patientId.getAssigningAuthority().getUniversalId(), patientId.getId()));
         fhirQuery.where(identifier);
     }