diff --git a/src/Driver/Quoter.php b/src/Driver/Quoter.php
index 8f0dd0a8..2515f548 100644
--- a/src/Driver/Quoter.php
+++ b/src/Driver/Quoter.php
@@ -136,7 +136,7 @@ public function quote(string $identifier, bool $isTable = false): string
     private function expression(string $identifier): string
     {
         return preg_replace_callback(
-            '/([a-z][0-9_a-z\.]*\(?)/i',
+            '/([_a-z][0-9_a-z\.]*\(?)/i',
             function ($match) {
                 $identifier = $match[1];
 
diff --git a/tests/Database/Functional/Driver/Common/Query/SelectQueryTest.php b/tests/Database/Functional/Driver/Common/Query/SelectQueryTest.php
index 90f69101..f9ac955b 100644
--- a/tests/Database/Functional/Driver/Common/Query/SelectQueryTest.php
+++ b/tests/Database/Functional/Driver/Common/Query/SelectQueryTest.php
@@ -2267,4 +2267,21 @@ public function testFragmentInWhereInClause(): void
             $select
         );
     }
+
+    /**
+     * Issue https://github.com/cycle/database/issues/49
+     */
+    public function testLeftJoinQuoting(): void
+    {
+        $select = $this->database
+            ->select()
+            ->from(['users'])
+            ->leftJoin('_1SCONST _1SCONST2(NOLOCK)')
+            ->on('SC3271.ID', '=', '_1SCONST2.OBJID');
+
+        $this->assertSameQuery(
+            'SELECT * FROM {users} LEFT JOIN {_1SCONST} _1SCONST2({NOLOCK}) ON {SC3271}.{ID} = {_1SCONST2}.{OBJID}',
+            $select
+        );
+    }
 }