diff --git a/tests/DOM/test_DOMImplementation.h b/tests/DOM/test_DOMImplementation.h
index 7c75697a..d2fa3658 100644
--- a/tests/DOM/test_DOMImplementation.h
+++ b/tests/DOM/test_DOMImplementation.h
@@ -25,9 +25,11 @@ class DOMImplementationTest : public TestCase
     {
       DOM::DOMImplementation<string_type> di;
       assert(di == 0);
+      assert(!di);
 
       DOM::DOMImplementation<string_type> di2 = SimpleDOM::DOMImplementation<string_type, string_adaptor>::getDOMImplementation();
       assert(di2 != 0);
+      assert(di2);
 
       assert(di != di2);
       assert(di2 != di);
diff --git a/tests/DOM/test_Document.h b/tests/DOM/test_Document.h
index 8d081ba0..714aed13 100644
--- a/tests/DOM/test_Document.h
+++ b/tests/DOM/test_Document.h
@@ -32,21 +32,26 @@ class DocumentTest : public TestCase
       assert(d == 0);
       assert(n == 0);
       assert(n == d);
+      assert(!d);
+      assert(!n);
     } // testNull
 
     void testAssignment()
     {
       DOM::Document<string_type> d = factory.createDocument(SA::construct_from_utf8(""), SA::construct_from_utf8(""), 0);
       assert(d != 0);
+      assert(d);
       assert(d.getNodeName() == SA::construct_from_utf8("#document"));
       assert(d.getNodeValue() == SA::construct_from_utf8(""));
 
       DOM::Node<string_type> n;
       assert(n == 0);
+      assert(!n);
       assert(n != d);
 
       n = d;
 
+      assert(n);
       assert(n == d);
       assert(d == DOM::Document<string_type>(n));