diff --git a/crates/db/src/vocab.rs b/crates/db/src/vocab.rs
index d2b33f8..389278a 100644
--- a/crates/db/src/vocab.rs
+++ b/crates/db/src/vocab.rs
@@ -39,10 +39,7 @@ where
         .fetch_optional(executor)
         .await?;
 
-    Ok(row.map(|r| Vocabulary {
-        id: VocabularyId::from_uuid(r.get("id")),
-        key: r.get("key"),
-    }))
+    row.map(map_vocabulary).transpose()
 }
 
 /// Insert a term and its labels. Multiple statements — pass a transaction
@@ -129,6 +126,13 @@ where
     Ok(found.map(|_| TermRef::new(term_id, vocabulary_id)))
 }
 
+fn map_vocabulary(row: sqlx::postgres::PgRow) -> Result<Vocabulary, sqlx::Error> {
+    Ok(Vocabulary {
+        id: VocabularyId::from_uuid(row.try_get("id")?),
+        key: row.try_get("key")?,
+    })
+}
+
 fn map_term(row: sqlx::postgres::PgRow) -> Result<Term, sqlx::Error> {
     let labels: sqlx::types::Json<Vec<LocalizedLabel>> = row.try_get("labels")?;
 
diff --git a/crates/db/tests/vocab.rs b/crates/db/tests/vocab.rs
index 48e32dd..69af596 100644
--- a/crates/db/tests/vocab.rs
+++ b/crates/db/tests/vocab.rs
@@ -73,6 +73,48 @@ async fn term_with_multilingual_labels_round_trips(pool: PgPool) {
     assert_eq!(listed[0].id, term_id);
 }
 
+#[sqlx::test]
+async fn term_with_no_labels_round_trips_empty(pool: PgPool) {
+    let db = Db::from_pool(pool);
+    let v = vocab::create_vocabulary(db.pool(), "material")
+        .await
+        .unwrap();
+
+    let mut tx = db.pool().begin().await.unwrap();
+    let term_id = vocab::add_term(
+        &mut *tx,
+        &NewTerm {
+            vocabulary_id: v.id,
+            external_uri: None,
+            labels: vec![],
+        },
+    )
+    .await
+    .unwrap();
+    tx.commit().await.unwrap();
+
+    let term = vocab::term_by_id(db.pool(), term_id)
+        .await
+        .unwrap()
+        .unwrap();
+    assert!(term.labels.is_empty());
+}
+
+#[sqlx::test]
+async fn duplicate_vocabulary_key_is_rejected(pool: PgPool) {
+    let db = Db::from_pool(pool);
+    vocab::create_vocabulary(db.pool(), "material")
+        .await
+        .unwrap();
+    let err = vocab::create_vocabulary(db.pool(), "material")
+        .await
+        .unwrap_err();
+    assert!(
+        matches!(err, sqlx::Error::Database(_)),
+        "expected a unique-violation DB error, got: {err:?}"
+    );
+}
+
 #[sqlx::test]
 async fn resolve_term_checks_vocabulary_membership(pool: PgPool) {
     let db = Db::from_pool(pool);