diff --git a/CHANGELOG b/CHANGELOG
index b99584966..c27d403d0 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,5 @@
+* Fix issue where certain versions of Safari treat class names case-insensitively in Selector/$$ queries. (Andrew Dupont, kangax, Brice)
+
 * Fix issue where Function#argumentNames returned incorrect results in IE when comments were intermixed with argument names. (Christophe Porteneuve, T.J. Crowder)
 
 * Performance improvements in Function methods (Samuel Lebeau, kangax, jddalton, Tobie Langel).
diff --git a/src/dom/selector.js b/src/dom/selector.js
index 9a8ff3fab..5ece49e3d 100644
--- a/src/dom/selector.js
+++ b/src/dom/selector.js
@@ -38,6 +38,8 @@ var Selector = Class.create({
   
   shouldUseSelectorsAPI: function() {
     if (!Prototype.BrowserFeatures.SelectorsAPI) return false;
+        
+    if (Selector.CASE_INSENSITIVE_CLASS_NAMES) return false;
     
     if (!Selector._div) Selector._div = new Element('div');
 
@@ -177,6 +179,25 @@ var Selector = Class.create({
   }
 });
 
+if (Prototype.BrowserFeatures.SelectorsAPI &&
+ document.compatMode === 'BackCompat') {
+  // Versions of Safari 3 before 3.1.2 treat class names case-insensitively in
+  // quirks mode. If we detect this behavior, we should use a different
+  // approach.
+  Selector.CASE_INSENSITIVE_CLASS_NAMES = (function(){
+    var div = document.createElement('div'),
+     span = document.createElement('span');
+
+    div.id = "prototype_test_id";
+    span.className = 'Test';
+    div.appendChild(span);
+    var isIgnored = (div.querySelector('#prototype_test_id .test') !== null);
+    div = span = null;
+    alert(isIgnored);
+    return isIgnored;
+  })();
+}
+
 Object.extend(Selector, {
   _cache: { },