diff --git a/CHANGELOG b/CHANGELOG
index dbeca92..79a7ea4 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,5 @@
+* Workaround a JavaScript exception in Opera. (Thomas Fuchs)
+
 * Improve NodeList detection for Safari's $A function. (Garrett Smith, jddalton)
 
 * Use different tactic to sniff for Opera in order to avoid false positives in IE. (Tobie Langel, jddalton)
diff --git a/src/dom.js b/src/dom.js
index 89e17ee..87bdbac 100644
--- a/src/dom.js
+++ b/src/dom.js
@@ -597,7 +597,7 @@ Element.Methods = {
 
     element = forElement;
     do {
-      if (!Prototype.Browser.Opera || element.tagName.toUpperCase() == 'BODY') {
+      if (!Prototype.Browser.Opera || (element.tagName && (element.tagName.toUpperCase() == 'BODY'))) {
         valueT -= element.scrollTop  || 0;
         valueL -= element.scrollLeft || 0;
       }