diff --git a/CHANGELOG b/CHANGELOG
index c580428..3806eed 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Define Node constants conditionally after checking for Node.ELEMENT_NODE presence.  Add unit test to check the values of all constants.  Closes #7625.  [Mislav Marohnić]
+
 * Make sure Enumerable#include doesn't do type comparision.  [Mislav Marohnić]
 
 * Add contextmenu to Event.DOMEvents.  [Thomas Fuchs]
diff --git a/src/dom.js b/src/dom.js
index e6ad889..f99c5d2 100644
--- a/src/dom.js
+++ b/src/dom.js
@@ -22,23 +22,25 @@ if (Prototype.BrowserFeatures.XPath) {
 
 /*--------------------------------------------------------------------------*/
 
-if (!window.Node)
-  var Node = { };
-  
-Object.extend(Node, {
-  ELEMENT_NODE: 1,
-  ATTRIBUTE_NODE: 2,
-  TEXT_NODE: 3,
-  CDATA_SECTION_NODE: 4,
-  ENTITY_REFERENCE_NODE: 5,
-  ENTITY_NODE: 6,
-  PROCESSING_INSTRUCTION_NODE: 7,
-  COMMENT_NODE: 8,
-  DOCUMENT_NODE: 9,
-  DOCUMENT_TYPE_NODE: 10,
-  DOCUMENT_FRAGMENT_NODE: 11,
-  NOTATION_NODE: 12
-});
+if (!window.Node) var Node = { };
+
+if (!Node.ELEMENT_NODE) {
+  // DOM level 2 ECMAScript Language Binding
+  Object.extend(Node, {
+    ELEMENT_NODE: 1,
+    ATTRIBUTE_NODE: 2,
+    TEXT_NODE: 3,
+    CDATA_SECTION_NODE: 4,
+    ENTITY_REFERENCE_NODE: 5,
+    ENTITY_NODE: 6,
+    PROCESSING_INSTRUCTION_NODE: 7,
+    COMMENT_NODE: 8,
+    DOCUMENT_NODE: 9,
+    DOCUMENT_TYPE_NODE: 10,
+    DOCUMENT_FRAGMENT_NODE: 11,
+    NOTATION_NODE: 12
+  });
+}
 
 (function() {
   var element = this.Element;
@@ -1211,4 +1213,4 @@ document.viewport = {
       window.pageXOffset || document.documentElement.scrollLeft || document.body.scrollLeft,
       window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop);
   }
-};
\ No newline at end of file
+};
diff --git a/test/unit/dom.html b/test/unit/dom.html
index a800a18..6058d15 100644
--- a/test/unit/dom.html
+++ b/test/unit/dom.html
@@ -1498,7 +1498,6 @@
       });
     }},
     
-    
     testViewportDimensions: function() {with(this) {
       window.resizeTo(800, 600);
       var before = document.viewport.getDimensions();
@@ -1521,6 +1520,29 @@
       assertEqual(25, document.viewport.getScrollOffsets().left);
       
       window.resizeTo(850, 650);
+    }},
+    
+    testNodeConstants: function() {with(this) {
+      assert(window.Node, 'window.Node is unavailable');
+
+      var constants = $H({
+        ELEMENT_NODE: 1,
+        ATTRIBUTE_NODE: 2,
+        TEXT_NODE: 3,
+        CDATA_SECTION_NODE: 4,
+        ENTITY_REFERENCE_NODE: 5,
+        ENTITY_NODE: 6,
+        PROCESSING_INSTRUCTION_NODE: 7,
+        COMMENT_NODE: 8,
+        DOCUMENT_NODE: 9,
+        DOCUMENT_TYPE_NODE: 10,
+        DOCUMENT_FRAGMENT_NODE: 11,
+        NOTATION_NODE: 12
+      });
+
+      constants.each(function(pair) {
+        assertEqual(Node[pair.key], pair.value);
+      }, this);
     }}
   }, 'testlog');