diff --git a/Makefile b/Makefile
index 5bb70d8..d701ac8 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@ clean:
 
 build: build/squire.js build/document.html
 
-build/squire.js: source/Node.js source/Range.js source/Editor.js
+build/squire.js: source/TreeWalker.js source/Node.js source/Range.js source/Editor.js
 	mkdir -p $(@D)
 	cat $^ | uglifyjs > $@
 
diff --git a/source/Node.js b/source/Node.js
index afc19f1..c92a425 100644
--- a/source/Node.js
+++ b/source/Node.js
@@ -50,53 +50,9 @@ var ELEMENT_NODE = 1,  // Node.ELEMENT_NODE,
     FILTER_ACCEPT = 1, // NodeFilter.FILTER_ACCEPT,
     FILTER_SKIP = 3;   // NodeFilter.FILTER_SKIP;
 
-var walkForward = function ( current, filter ) {
-    var node;
-    while ( true ) {
-        node = current.firstChild;
-        while ( !node && current ) {
-            node = current.nextSibling;
-            if ( !node ) {
-                current = current.parentNode;
-            }
-        }
-
-        if ( !node ) {
-            return null;
-        }
-        if ( filter( node ) ) {
-            return node;
-        }
-
-        current = node;
-    }
+var isBlock = function ( el ) {
+    return el.isBlock() ? FILTER_ACCEPT : FILTER_SKIP;
 };
-
-var walkBackward = function ( current, filter ) {
-    var node;
-    while ( true ) {
-        node = current.previousSibling;
-        if ( node ) {
-            while ( current = node.lastChild ) {
-                node = current;
-            }
-        } else {
-            node = current.parentNode;
-        }
-
-        if ( node.nodeName === 'BODY' ||
-                node.nodeType === DOCUMENT_FRAGMENT_NODE ) {
-            return null;
-        }
-        if ( filter( node ) ) {
-            return node;
-        }
-
-        current = node;
-    }
-};
-
-var isBlock = function ( el ) { return el.isBlock(); };
 var useTextFixer = !!( window.opera || window.ie );
 
 implement( Node, {
@@ -127,10 +83,18 @@ implement( Node, {
         return parent ? parent.nearest( tag, attributes ) : null;
     },
     getPreviousBlock: function () {
-        return walkBackward( this, isBlock );
+        var doc = this.ownerDocument,
+            walker = doc.createTreeWalker(
+                doc.body, SHOW_ELEMENT, isBlock, false );
+        walker.currentNode = this;
+        return walker.previousNode();
     },
     getNextBlock: function () {
-        return walkForward( this, isBlock );
+        var doc = this.ownerDocument,
+            walker = doc.createTreeWalker(
+                doc.body, SHOW_ELEMENT, isBlock, false );
+        walker.currentNode = this;
+        return walker.nextNode();
     },
     split: function ( node, stopCondition ) {
         return node;
diff --git a/source/TreeWalker.js b/source/TreeWalker.js
new file mode 100644
index 0000000..20d8569
--- /dev/null
+++ b/source/TreeWalker.js
@@ -0,0 +1,133 @@
+/* Copyright © 2011 by Neil Jenkins. Licensed under the MIT license. */
+
+( function ( doc ) {
+
+/*global document, window */
+
+"use strict";
+
+// ---
+
+var needsReplacement = !doc.createTreeWalker;
+
+// IE9 sometimes throws errors when calling TreeWalker#nextNode or
+// TreeWalker#previousNode. No way to feature detect this.
+if ( window.ie === 9 ) {
+    needsReplacement = true;
+}
+
+// Feature detect Opera bug in TreeWalker#previousNode
+if ( !needsReplacement ) {
+    ( function () {
+    var div = doc.createElement( 'div' ),
+        text = doc.createTextNode( '' );
+    
+    div.appendChild( text );
+    
+    var div1 = div.cloneNode( true ),
+        div2 = div.cloneNode( true ),
+        div3 = div.cloneNode( true ),
+        walker = doc.createTreeWalker( div, 1, function ( node ) {
+            return 1;
+        }, false );
+    div.appendChild( div1 );
+    div.appendChild( div2 );
+    div.appendChild( div3 );
+    walker.currentNode = div3;
+    if ( walker.previousNode() !== div2 ) {
+        needsReplacement = true;
+    }
+    }() );
+}
+
+if ( !needsReplacement ) { return; }
+
+// ---
+
+var typeToBitArray = {
+    // ELEMENT_NODE
+    1: 1,
+    // ATTRIBUTE_NODE
+    2: 2,
+    // TEXT_NODE
+    3: 4,
+    // COMMENT_NODE
+    8: 128,
+    // DOCUMENT_NODE
+    9: 256,
+    // DOCUMENT_FRAGMENT_NODE
+    11: 1024
+};
+
+var FILTER_ACCEPT = 1;
+
+var TreeWalker = function ( root, nodeType, filter ) {
+    this.root = this.currentNode = root;
+    this.nodeType = nodeType;
+    this.filter = filter;
+};
+
+TreeWalker.prototype.nextNode = function () {
+    var current = this.currentNode,
+        root = this.root,
+        nodeType = this.nodeType,
+        filter = this.filter,
+        node;
+    while ( true ) {
+        node = current.firstChild;
+        while ( !node && current ) {
+            node = current.nextSibling;
+            if ( !node ) {
+                current = current.parentNode;
+                if ( current === root ) {
+                    return null;
+                }
+            }
+        }
+
+        if ( !node ) {
+            return null;
+        }
+        if ( ( typeToBitArray[ node.nodeType ] & nodeType ) &&
+                filter( node ) === FILTER_ACCEPT ) {
+            this.currentNode = node;
+            return node;
+        }
+
+        current = node;
+    }
+};
+
+TreeWalker.prototype.previousNode = function () {
+    var current = this.currentNode,
+        root = this.root,
+        nodeType = this.nodeType,
+        filter = this.filter,
+        node;
+    while ( true ) {
+        if ( node === root ) {
+            return null;
+        }
+        node = current.previousSibling;
+        if ( node ) {
+            while ( current = node.lastChild ) {
+                node = current;
+            }
+        } else {
+            node = current.parentNode;
+        }
+        if ( ( typeToBitArray[ node.nodeType ] & nodeType ) &&
+                filter( node ) === FILTER_ACCEPT ) {
+            this.currentNode = node;
+            return node;
+        }
+
+        current = node;
+    }
+};
+
+doc.createTreeWalker = function ( root, nodeType, filter ) {
+    return new TreeWalker( root, nodeType, filter );
+};
+
+}( document ) );
\ No newline at end of file