diff --git a/program/lib/Roundcube/rcube_db_mssql.php b/program/lib/Roundcube/rcube_db_mssql.php
index 3c1b9d71f..726e4b421 100644
--- a/program/lib/Roundcube/rcube_db_mssql.php
+++ b/program/lib/Roundcube/rcube_db_mssql.php
@@ -52,7 +52,7 @@ class rcube_db_mssql extends rcube_db
     protected function conn_configure($dsn, $dbh)
     {
         // Set date format in case of non-default language (#1488918)
-        $this->query("SET DATEFORMAT ymd");
+        $dbh->query("SET DATEFORMAT ymd");
     }
 
     /**
diff --git a/program/lib/Roundcube/rcube_db_mysql.php b/program/lib/Roundcube/rcube_db_mysql.php
index 24f9ce1bd..d3d0ac5c8 100644
--- a/program/lib/Roundcube/rcube_db_mysql.php
+++ b/program/lib/Roundcube/rcube_db_mysql.php
@@ -60,7 +60,7 @@ class rcube_db_mysql extends rcube_db
      */
     protected function conn_configure($dsn, $dbh)
     {
-        $this->query("SET NAMES 'utf8'");
+        $dbh->query("SET NAMES 'utf8'");
     }
 
     /**
diff --git a/program/lib/Roundcube/rcube_db_pgsql.php b/program/lib/Roundcube/rcube_db_pgsql.php
index d72c9d6b3..68bf6d85d 100644
--- a/program/lib/Roundcube/rcube_db_pgsql.php
+++ b/program/lib/Roundcube/rcube_db_pgsql.php
@@ -36,7 +36,7 @@ class rcube_db_pgsql extends rcube_db
      */
     protected function conn_configure($dsn, $dbh)
     {
-        $this->query("SET NAMES 'utf8'");
+        $dbh->query("SET NAMES 'utf8'");
     }
 
     /**
diff --git a/program/lib/Roundcube/rcube_db_sqlsrv.php b/program/lib/Roundcube/rcube_db_sqlsrv.php
index 45c41cdaf..4339f3dfd 100644
--- a/program/lib/Roundcube/rcube_db_sqlsrv.php
+++ b/program/lib/Roundcube/rcube_db_sqlsrv.php
@@ -52,7 +52,7 @@ class rcube_db_sqlsrv extends rcube_db
     protected function conn_configure($dsn, $dbh)
     {
         // Set date format in case of non-default language (#1488918)
-        $this->query("SET DATEFORMAT ymd");
+        $dbh->query("SET DATEFORMAT ymd");
     }
 
     /**