diff --git a/CHANGELOG b/CHANGELOG
index 30d8787..b54b0c0 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Array.prototype.uniq optimization.  Closes #7417.  [Christophe Porteneuve]
+
 * String.prototype.endsWith should not fail on multiple occurrences.  Closes #7416.  [Christophe Porteneuve]
 
 * Add Form.Methods.request as a convenience method for serializing and submitting a form via Ajax.Request to the URL in the form's action attribute.  [sam]
diff --git a/src/array.js b/src/array.js
index a594f97..dbf036d 100644
--- a/src/array.js
+++ b/src/array.js
@@ -68,9 +68,11 @@ Object.extend(Array.prototype, {
     return this.length > 1 ? this : this[0];
   },
   
-  uniq: function() {
-    return this.inject([], function(array, value) {
-      return array.include(value) ? array : array.concat([value]);
+  uniq: function(sorted) {
+    return this.inject([], function(array, value, index) {
+      if (0 == index || (sorted ? array.last() != value : !array.include(value)))
+        array.push(value);
+      return array;
     });
   },
   
diff --git a/test/unit/array.html b/test/unit/array.html
index 6c0cc55..f8518ff 100644
--- a/test/unit/array.html
+++ b/test/unit/array.html
@@ -127,6 +127,7 @@
       assertEnumEqual([1], [1].uniq());
       assertEnumEqual([], [].uniq());
       assertEnumEqual([0, 1, 2, 3], [0, 1, 2, 2, 3, 0, 2].uniq());
+      assertEnumEqual([0, 1, 2, 3], [0, 0, 1, 1, 2, 3, 3, 3].uniq(true));
     }},
     
     testWithout: function(){ with(this) {