diff --git a/src/Rct567/DomQuery/DomQuery.php b/src/Rct567/DomQuery/DomQuery.php
index 24d01ef..aad550f 100644
--- a/src/Rct567/DomQuery/DomQuery.php
+++ b/src/Rct567/DomQuery/DomQuery.php
@@ -555,6 +555,8 @@ public function not($selector)
                         $result->addDomNode($node);
                     }
                 }
+            } elseif ($selector === null) {
+                $result->addDomNodes($this->nodes);
             } else {
                 $selection = self::create($this->document)->find($selector);
 
@@ -591,7 +593,7 @@ public function not($selector)
     public function add($selector, $context=null)
     {
         $result = $this->createChildInstance();
-        $result->nodes = $this->nodes;
+        $result->addDomNodes($this->nodes);
 
         $selection = $this->getTargetResult($selector, $context);
 
@@ -628,6 +630,8 @@ public function filter($selector)
                         $result->addDomNode($node);
                     }
                 }
+            } elseif ($selector === null) {
+                $result->addDomNodes($this->nodes);
             } else {
                 $selection = self::create($this->document)->find($selector);
 
@@ -741,7 +745,7 @@ public function has($selector)
     {
         $result = $this->createChildInstance();
 
-        if ($this->length > 0) {
+        if ($this->length > 0 && $selector !== null) {
             foreach ($this as $node) {
                 if ($node->find($selector)->length > 0) {
                     $result->addDomNode($node->get(0));
diff --git a/src/Rct567/DomQuery/DomQueryNodes.php b/src/Rct567/DomQuery/DomQueryNodes.php
index fa9b269..eb11abf 100644
--- a/src/Rct567/DomQuery/DomQueryNodes.php
+++ b/src/Rct567/DomQuery/DomQueryNodes.php
@@ -317,7 +317,33 @@ public function loadDomNodeList(\DOMNodeList $dom_node_list, $prepend=false)
     }
 
     /**
-     * Add node to result set.
+     * Add an array of nodes to the result set.
+     *
+     * @param \DOMNode[] $dom_nodes
+     *
+     * @return void
+     */
+    public function addDomNodes(array $dom_nodes)
+    {
+        if (!isset($dom_nodes[0])) {
+            return;
+        }
+
+        foreach ($dom_nodes as $dom_node) {
+            $this->nodes[] = $dom_node;
+        }
+
+        $this->length = \count($this->nodes);
+
+        if ($dom_nodes[0] instanceof \DOMDocument) {
+            $this->setDomDocument($dom_nodes[0]);
+        } else {
+            $this->setDomDocument($dom_nodes[0]->ownerDocument);
+        }
+    }
+
+    /**
+     * Add a single node to the result set.
      *
      * @param \DOMNode $dom_node
      * @param bool $prepend
@@ -327,7 +353,7 @@ public function loadDomNodeList(\DOMNodeList $dom_node_list, $prepend=false)
     public function addDomNode(\DOMNode $dom_node, $prepend=false)
     {
         if ($prepend) {
-            array_unshift($this->nodes, $dom_node);
+            \array_unshift($this->nodes, $dom_node);
         } else {
             $this->nodes[] = $dom_node;
         }
diff --git a/tests/Rct567/DomQuery/Tests/DomQueryTraversingFilterTest.php b/tests/Rct567/DomQuery/Tests/DomQueryTraversingFilterTest.php
index ff14a95..a90a88c 100644
--- a/tests/Rct567/DomQuery/Tests/DomQueryTraversingFilterTest.php
+++ b/tests/Rct567/DomQuery/Tests/DomQueryTraversingFilterTest.php
@@ -36,6 +36,7 @@ public function testHas()
         $this->assertEquals('<a class="x"><span id="here"><u></u></span></a>', (string) $dom->find('a')->has('span > u'));
         $this->assertEquals('<a class="x"><span id="here"><u></u></span></a>', (string) $dom->find('a')->has($dom->find('#here')));
         $this->assertEquals('<a class="x"><span id="here"><u></u></span></a>', (string) $dom->find('a')->has($dom->find('#here')->get(0))); # by DOMNode
+        $this->assertEquals(0, (string) $dom->find('a')->has(null)->length);
     }
 
     /*
@@ -57,6 +58,8 @@ public function testFilter()
         $this->assertEquals('<a class="xpp"></a>', (string) $selection->filter($dom->find('a.xpp')));
         $this->assertEquals('<a class="x"></a>', (string) $selection->filter($dom->find('a')->get(-2))); // filter by DOMNode
         $this->assertEquals('<header>2</header>', (string) $dom->find('*')->filter('header'));
+        $this->assertEquals(2, $dom->find('a[class]')->filter(null)->length);
+        $this->assertEquals('<a class="x"></a><a class="xpp"></a>', (string) $dom->find('a[class]')->filter(null));
     }
 
     /*
@@ -68,6 +71,7 @@ public function testNot()
         $selection = $dom->find('a');
         $this->assertEquals(5, $selection->length);
         $this->assertEquals(5, $selection->not('p')->length);
+        $this->assertEquals((string) $selection, (string) $selection->not(null));
         $this->assertEquals(0, $selection->not('a')->length);
         $this->assertEquals(4, $selection->not('#mmm')->length);
         $this->assertEquals(3, $selection->not('#mmm')->not('.xpp')->length);