diff --git a/lib/Database.php b/lib/Database.php
index 812012f..1373c9a 100644
--- a/lib/Database.php
+++ b/lib/Database.php
@@ -1193,12 +1193,10 @@ class Database {
         }
         $id = $this->articleValidateId($user, $id)['article'];
         $out = $this->db->prepare("SELECT id,name from arsse_labels where owner = ? and exists(select id from arsse_label_members where article = ? and label = arsse_labels.id and assigned = 1)", "str", "int")->run($user, $id)->getAll();
-        if (!$out) {
-            return $out;
-        } else {
-            // flatten the result to return just the label ID or name
-            return array_column($out, !$byName ? "id" : "name");
-        }
+        // flatten the result to return just the label ID or name, sorted
+        $out = $out ? array_column($out, !$byName ? "id" : "name") : [];
+        sort($out);
+        return $out;
     }
 
     public function articleCategoriesGet(string $user, $id): array {
@@ -1444,7 +1442,7 @@ class Database {
         $this->labelValidateId($user, $id, $byName, false);
         $field = !$byName ? "id" : "name";
         $type = !$byName ? "int" : "str";
-        $out = $this->db->prepare("SELECT article from arsse_label_members join arsse_labels on label = id where assigned = 1 and $field = ? and owner = ?", $type, "str")->run($id, $user)->getAll();
+        $out = $this->db->prepare("SELECT article from arsse_label_members join arsse_labels on label = id where assigned = 1 and $field = ? and owner = ? order by article", $type, "str")->run($id, $user)->getAll();
         if (!$out) {
             // if no results were returned, do a full validation on the label ID
             $this->labelValidateId($user, $id, $byName, true, true);
diff --git a/lib/Db/PDOError.php b/lib/Db/PDOError.php
index 5aee4df..7e8252d 100644
--- a/lib/Db/PDOError.php
+++ b/lib/Db/PDOError.php
@@ -19,6 +19,7 @@ trait PDOError {
                 return [ExceptionInput::class, 'engineTypeViolation', $err[2]];
             case "23000":
             case "23502":
+            case "23505":
                 return [ExceptionInput::class, "constraintViolation", $err[2]];
             case "55P03":
             case "57014":
diff --git a/tests/cases/Database/SeriesArticle.php b/tests/cases/Database/SeriesArticle.php
index 05a8ded..2147d64 100644
--- a/tests/cases/Database/SeriesArticle.php
+++ b/tests/cases/Database/SeriesArticle.php
@@ -957,7 +957,7 @@ trait SeriesArticle {
     }
 
     public function testListTheLabelsOfAnArticle() {
-        $this->assertEquals([2,1], Arsse::$db->articleLabelsGet("john.doe@example.com", 1));
+        $this->assertEquals([1,2], Arsse::$db->articleLabelsGet("john.doe@example.com", 1));
         $this->assertEquals([2], Arsse::$db->articleLabelsGet("john.doe@example.com", 5));
         $this->assertEquals([], Arsse::$db->articleLabelsGet("john.doe@example.com", 2));
         $this->assertEquals(["Fascinating","Interesting"], Arsse::$db->articleLabelsGet("john.doe@example.com", 1, true));
diff --git a/tests/cases/Db/PostgreSQL/TestDatabase.php b/tests/cases/Db/PostgreSQL/TestDatabase.php
index 2b6e7fb..91e326f 100644
--- a/tests/cases/Db/PostgreSQL/TestDatabase.php
+++ b/tests/cases/Db/PostgreSQL/TestDatabase.php
@@ -14,7 +14,7 @@ class TestDatabase extends \JKingWeb\Arsse\TestCase\Database\Base {
     protected static $implementation = "PDO PostgreSQL";
 
     protected function nextID(string $table): int {
-        return ((int) static::$drv->query("SELECT last_value from pg_sequences where sequencename = '{$table}_id_seq'")->getValue()) + 1;
+        return (int) static::$drv->query("SELECT coalesce(last_value, (select max(id) from $table)) + 1 from pg_sequences where sequencename = '{$table}_id_seq'")->getValue();
     }
 
     public function setUp() {
@@ -30,7 +30,7 @@ class TestDatabase extends \JKingWeb\Arsse\TestCase\Database\Base {
                 and column_default like 'nextval(%'
             ";
         foreach(static::$drv->query($seqList) as $r) {
-            $num = static::$drv->query("SELECT max({$r['col']}) from {$r['table']}")->getValue();
+            $num = (int) static::$drv->query("SELECT max({$r['col']}) from {$r['table']}")->getValue();
             if (!$num) {
                 continue;
             }