diff --git a/carddav.php b/carddav.php
index a0b87372..b0ca3546 100644
--- a/carddav.php
+++ b/carddav.php
@@ -206,7 +206,11 @@ public function inputValue(string $id, bool $allowHtml, int $source = rcube_util
     public function showMessage(string $msg, string $msgType = 'notice', bool $override = false, int $timeout = 0): void
     {
         $rcube = rcube::get_instance();
-        $rcube->output->show_message($msg, $msgType, null, $override, $timeout);
+        $output = $rcube->output;
+
+        if ($output instanceof rcmail_output) {
+            $output->show_message($msg, $msgType, null, $override, $timeout);
+        }
     }
 
     public function clientCommand(string $method, ...$arguments): void
diff --git a/src/Addressbook.php b/src/Addressbook.php
index 46833a31..d4cefafd 100644
--- a/src/Addressbook.php
+++ b/src/Addressbook.php
@@ -448,7 +448,7 @@ public function get_record($id, $assoc = false)
      * @param ?string $sort_order Sort order
      */
     // phpcs:ignore PSR1.Methods.CamelCapsMethodName -- method name defined by rcube_addressbook class
-    public function set_sort_order($sort_col, $sort_order = null): void
+    public function set_sort_order($sort_col = null, $sort_order = null): void
     {
         if (isset($sort_col) && key_exists($sort_col, $this->coltypes)) {
             $this->sort_col = $sort_col;
@@ -564,8 +564,8 @@ public function update($id, $save_cols)
     /**
      * Mark one or more contact records as deleted
      *
-     * @param array $ids   Record identifiers
-     * @param bool  $force Remove records irreversible (see self::undelete)
+     * @param array|string $ids   Record identifiers
+     * @param bool         $force Remove records irreversible (see self::undelete)
      *
      * @return int|false Number of removed records, False on failure
      */
@@ -575,6 +575,10 @@ public function delete($ids, $force = true)
         $logger = $infra->logger();
         $db = $infra->db();
 
+        if (is_string($ids)) {
+            $ids = explode(self::SEPARATOR, $ids);
+        }
+
         /** @var list<string> $ids */
         $deleted = 0;
         $logger->info("delete([" . implode(",", $ids) . "])");
@@ -691,7 +695,7 @@ public function delete_all($with_groups = false): void
      * This filter mechanism is applied in addition to other filter mechanisms, see the description of the count()
      * operation.
      *
-     * @param null|0|string $group_id Database identifier of the group. 0/"0"/null to reset the group filter.
+     * @param null|int|string $group_id Database identifier of the group. 0/"0"/null to reset the group filter.
      */
     // phpcs:ignore PSR1.Methods.CamelCapsMethodName -- method name defined by rcube_addressbook class
     public function set_group($group_id): void
@@ -703,6 +707,7 @@ public function set_group($group_id): void
             $logger->debug("set_group($group_id)");
 
             if ($group_id) {
+                $group_id = (string) $group_id;
                 $db = $infra->db();
                 // check for valid ID with the database - this throws an exception if the group cannot be found
                 $db->lookup(["id" => $group_id, "abook_id" => $this->id], ["id"], "groups");
@@ -994,9 +999,7 @@ public function add_to_group($group_id, $ids): int
             $davAbook = $this->getCardDavObj();
 
             if (is_string($ids)) {
-                $ids_string = $ids;
-                /** @psalm-var list<string> $ids */
-                $ids = explode(self::SEPARATOR, $ids_string);
+                $ids = explode(self::SEPARATOR, $ids);
             }
 
             $db->startTransaction();
diff --git a/src/Config.php b/src/Config.php
index 4e6c394d..36d9d807 100644
--- a/src/Config.php
+++ b/src/Config.php
@@ -84,7 +84,7 @@ public function __construct()
         $this->admPrefs = new AdminSettings(__DIR__ . '/../config.inc.php', $this->logger, $this->httpLogger);
 
         $rcube = rcube::get_instance();
-        $this->db = new Database($this->logger, $rcube->db);
+        $this->db = new Database($this->logger, $rcube->get_dbh());
     }
 
     public function db(): AbstractDatabase
diff --git a/tests/DBInteroperability/DatabaseTest.php b/tests/DBInteroperability/DatabaseTest.php
index d86dc1e1..f35c8423 100644
--- a/tests/DBInteroperability/DatabaseTest.php
+++ b/tests/DBInteroperability/DatabaseTest.php
@@ -497,13 +497,13 @@ public function connectToDbErrFuncProvider(): array
     public function testExceptionOnFailureToConnectToDb($errFunc): void
     {
         if ($GLOBALS["TEST_DBTYPE"] == "sqlite3") {
-            $dbh = \rcube_db::factory("sqlite:///" . __DIR__ . "/../../testreports/does/not/doesNotExist.db");
+            $dbh = \rcube_db::factory("sqlite:////does/not/doesNotExist.db");
             $expErrMsg = 'doesNotExist.db';
         } elseif ($GLOBALS["TEST_DBTYPE"] == "postgres") {
-            $dbh = \rcube_db::factory("pgsql://a@unix(" . __DIR__ . "/../../testreports/does/not/doesNotExist)/db");
+            $dbh = \rcube_db::factory("pgsql://a@unix(/does/not/doesNotExist)/db");
             $expErrMsg = 'doesNotExist';
         } elseif ($GLOBALS["TEST_DBTYPE"] == "mysql") {
-            $dbh = \rcube_db::factory("mysql://a@unix(" . __DIR__ . "/../../testreports/does/not/doesNotExist)/db");
+            $dbh = \rcube_db::factory("mysql://a@unix(/does/not/doesNotExist)/db");
             $expErrMsg = 'No such file or directory';
         } else {
             $this->fail("unsupported DB");