diff --git a/CHANGELOG b/CHANGELOG
index 0476ff7..1a98cf8 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Roll back the fix for #9609, since it does not work in Opera. Instead, avoid using "valueOf" or "toString" as field names in forms.
+
 * Prevent DOM node expandos _countedByPrototype and _prototypeEventID from being serialized into (inner|outer)HTML in IE. Closes #10909. [dcpedit, Tobie Langel, Andrew Dupont]
 
 * Make Ajax.Request#isSameOrigin JavaScript Lint compliant. [Andrew Dupont]
diff --git a/src/form.js b/src/form.js
index 78c03ff..0fd2ef3 100644
--- a/src/form.js
+++ b/src/form.js
@@ -14,7 +14,7 @@ var Form = {
         key = element.name; value = $(element).getValue();
         if (value != null && (element.type != 'submit' || (!submitted &&
             submit !== false && (!submit || key == submit) && (submitted = true)))) { 
-          if (key in result && !Object.isFunction(result[key])) {
+          if (key in result) {
             // a key is already present; construct an array of values
             if (!Object.isArray(result[key])) result[key] = [result[key]];
             result[key].push(value);
diff --git a/test/unit/form.html b/test/unit/form.html
index 14a3fbb..3e8aaec 100644
--- a/test/unit/form.html
+++ b/test/unit/form.html
@@ -125,11 +125,6 @@
       <input type="submit" id="ffe_ti2_submit" tabindex="1" />
     </form>
     
-    <form id="trouble_form">
-    	<input type="text" name="length" value="foo" />
-    	<input type="text" name="toString" value="55" />
-    	<input type="text" name="valueOf" value="bar" />
-    </form>
   </div>
 
   <!-- Tests follow -->
@@ -407,9 +402,6 @@
       assertHashEqual({ val1:4, action:'blah' },
                       $('form').serialize({ submit: 'inexistent' }));
                       
-      // try to serialize form containing toString, valueOf and length -named elements
-      assertHashEqual({ length: 'foo', toString: 55, valueOf: 'bar' },
-                      $('trouble_form').serialize(true));
     }},
     
     testFormMethodsOnExtendedElements: function() {with(this) {