diff --git a/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonTreeImporter.java b/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonTreeImporter.java
index 4cf1f55f..26ae0dcd 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonTreeImporter.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonTreeImporter.java
@@ -88,6 +88,9 @@ public class PersonTreeImporter {
     private int createRelationships(JsonNode relationships, Map<String, UUID> idByRowId) {
         int created = 0;
         for (JsonNode node : relationships) {
+            // Trap: a relationship node's personId / relatedPersonId fields carry the tree's
+            // local rowId (e.g. "row_a"), NOT a person slug. They are resolved through
+            // idByRowId to the upserted person's UUID.
             UUID person = idByRowId.get(text(node, "personId"));
             UUID related = idByRowId.get(text(node, "relatedPersonId"));
             if (person == null || related == null) {
diff --git a/backend/src/main/java/org/raddatz/familienarchiv/person/PersonService.java b/backend/src/main/java/org/raddatz/familienarchiv/person/PersonService.java
index 82de40b5..d2e894bf 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/person/PersonService.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/person/PersonService.java
@@ -163,8 +163,8 @@ public class PersonService {
         existing.setFirstName(preferHuman(existing.getFirstName(), cmd.firstName()));
         existing.setLastName(preferHuman(existing.getLastName(), cmd.lastName()));
         existing.setNotes(preferHuman(existing.getNotes(), cmd.notes()));
-        if (existing.getBirthYear() == null) existing.setBirthYear(cmd.birthYear());
-        if (existing.getDeathYear() == null) existing.setDeathYear(cmd.deathYear());
+        existing.setBirthYear(preferHuman(existing.getBirthYear(), cmd.birthYear()));
+        existing.setDeathYear(preferHuman(existing.getDeathYear(), cmd.deathYear()));
         if (cmd.personType() != null && existing.getPersonType() == PersonType.PERSON) {
             existing.setPersonType(cmd.personType());
         }
@@ -180,10 +180,16 @@ public class PersonService {
         return existing;
     }
 
+    // preferHuman keeps an existing human-entered value and only falls back to the canonical
+    // value when the existing one is absent — the single idiom for every fill-blank field.
     private static String preferHuman(String existing, String canonical) {
         return (existing == null || existing.isBlank()) ? blankToNull(canonical) : existing;
     }
 
+    private static Integer preferHuman(Integer existing, Integer canonical) {
+        return existing != null ? existing : canonical;
+    }
+
     private static String blankToNull(String s) {
         return (s == null || s.isBlank()) ? null : s.trim();
     }
diff --git a/backend/src/test/java/org/raddatz/familienarchiv/person/PersonImportUpsertTest.java b/backend/src/test/java/org/raddatz/familienarchiv/person/PersonImportUpsertTest.java
index 75a6381a..c8b81b2b 100644
--- a/backend/src/test/java/org/raddatz/familienarchiv/person/PersonImportUpsertTest.java
+++ b/backend/src/test/java/org/raddatz/familienarchiv/person/PersonImportUpsertTest.java
@@ -97,6 +97,26 @@ class PersonImportUpsertTest {
         assertThat(result.getNotes()).isEqualTo("Nichte von Herbert");
     }
 
+    @Test
+    void upsertBySourceRef_fillsBlankYears_butPreservesHumanEditedYears_onReimport() {
+        // Existing has a human-set birthYear and a blank deathYear.
+        Person existing = Person.builder()
+                .id(UUID.randomUUID()).sourceRef("clara-cram")
+                .lastName("Cram").birthYear(1890).deathYear(null).build();
+        when(personRepository.findBySourceRef("clara-cram")).thenReturn(Optional.of(existing));
+        when(personRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+
+        PersonUpsertCommand cmd = PersonUpsertCommand.builder()
+                .sourceRef("clara-cram").lastName("Cram")
+                .birthYear(1888).deathYear(1965)
+                .personType(PersonType.PERSON).provisional(false).build();
+
+        Person result = personService.upsertBySourceRef(cmd);
+
+        assertThat(result.getBirthYear()).isEqualTo(1890); // human value kept
+        assertThat(result.getDeathYear()).isEqualTo(1965); // blank filled from canonical
+    }
+
     @Test
     void upsertBySourceRef_neverFlipsProvisionalBackToTrue_onceHumanConfirmed() {
         // A human confirmed this provisional importer-created person (provisional -> false).