diff --git a/Foundation/CPArray.j b/Foundation/CPArray.j
index ffc056c7f..f0908805d 100755
--- a/Foundation/CPArray.j
+++ b/Foundation/CPArray.j
@@ -814,10 +814,7 @@ CPEnumerationReverse    = 1 << 1;
 */
 - (CPArray)arrayByAddingObject:(id)anObject
 {
-    var array = [self copy];
-    array.push(anObject);
-
-    return array;
+    return self.concat(anObject);
 }
 
 /*!
@@ -826,7 +823,7 @@ CPEnumerationReverse    = 1 << 1;
 */
 - (CPArray)arrayByAddingObjectsFromArray:(CPArray)anArray
 {
-    return slice(0).concat(anArray);
+    return self.concat(anArray);
 }
 
 /*
diff --git a/Foundation/CPKeyValueCoding.j b/Foundation/CPKeyValueCoding.j
index 1dfca2f54..b6012e75b 100644
--- a/Foundation/CPKeyValueCoding.j
+++ b/Foundation/CPKeyValueCoding.j
@@ -356,6 +356,12 @@ var CPObjectAccessorsForClassKey            = @"$CPObjectAccessorsForClassKey",
     SEL _memberOfSelector;
 }
 
+// This allows things like setByAddingObject: to work (since they use [[self class] alloc] internally).
+- (id)initWithObjects:(CPArray)objects count:(CPUInteger)aCount
+{
+    return [[CPSet alloc] initWithObjects:objects count:aCount];
+}
+
 - (id)initWithTarget:(id)aTarget key:(CPString)aKey
 {
     self = [super initWithObjects:nil count:0];
@@ -368,7 +374,7 @@ var CPObjectAccessorsForClassKey            = @"$CPObjectAccessorsForClassKey",
 
         _countOfSelector = CPSelectorFromString("countOf" + capitalizedKey);
         _enumeratorOfSelector = CPSelectorFromString("enumeratorOf" + capitalizedKey);
-        _memberOfSelector = CPSelectorFromString("memberOf" + capitalizedKey);
+        _memberOfSelector = CPSelectorFromString("memberOf" + capitalizedKey + ":");
     }
 
     return self;
diff --git a/Foundation/CPSet.j b/Foundation/CPSet.j
index 9563291f1..d6aef74ae 100644
--- a/Foundation/CPSet.j
+++ b/Foundation/CPSet.j
@@ -102,6 +102,21 @@
     return [[self alloc] initWithSet:set];
 }
 
+- (id)setByAddingObject:(id)anObject
+{
+    return [[self class] setWithArray:[[self allObjects] arrayByAddingObject:anObject]];
+}
+
+- (id)setByAddingObjectsFromSet:(CPSet)aSet
+{
+    return [self setByAddingObjectsFromArray:[aSet allObjects]];
+}
+
+- (id)setByAddingObjectsFromArray:(CPArray)anArray
+{
+    return [[self class] setWithArray:[[self allObjects] arrayByAddingObjectsFromArray:anArray]];
+}
+
 /*
     Basic initializer, returns an empty set
 */
diff --git a/Tests/Foundation/CPKeyValueCodingTest.j b/Tests/Foundation/CPKeyValueCodingTest.j
index 909ea8021..7719d13c2 100644
--- a/Tests/Foundation/CPKeyValueCodingTest.j
+++ b/Tests/Foundation/CPKeyValueCodingTest.j
@@ -612,3 +612,76 @@ var accessIVARS = YES;
 }
 
 @end
+
+
+@implementation UnorderedAccessorClass : CPObject
+{
+}
+
+- (id)memberOfObjects:(id)anObject
+{
+    if ([[0, 1, 3, 5, 7] indexOfObjectIdenticalTo:anObject] !== CPNotFound)
+        return anObject;
+
+    return nil;
+}
+
+- (CPEnumerator)enumeratorOfObjects
+{
+    return [[0, 1, 3, 5, 7] objectEnumerator];
+}
+
+- (CPUInteger)countOfObjects
+{
+    return 5;
+}
+
+@end
+
+@implementation CPKeyValueCodingTest (UnorderedAccessorPattern)
+
+- (void)testUnorderedAccessorPattern
+{
+    var object = [UnorderedAccessorClass new],
+        set = [object valueForKey:@"objects"];
+
+    [self assert:set equals:[CPSet setWithObjects:0, 1, 3, 5, 7]];
+
+    [self assertTrue:[set containsObject:0]];
+    [self assertTrue:[set containsObject:1]];
+    [self assertTrue:[set containsObject:3]];
+    [self assertTrue:[set containsObject:5]];
+    [self assertTrue:[set containsObject:7]];
+
+    [self assertFalse:[set containsObject:2]];
+    [self assertFalse:[set containsObject:4]];
+    [self assertFalse:[set containsObject:6]];
+    [self assertFalse:[set containsObject:8]];
+    [self assertFalse:[set containsObject:10]];
+
+    [self   assert:[set setByAddingObjectsFromArray:[2, 3, 4, 5, 6]]
+            equals:[CPSet setWithObjects:0, 1, 2, 3, 4, 5, 6, 7]];
+}
+
+- (void)testObjectsAtIndexes_
+{
+    var object = [ObjectsAtIndexesClass new],
+        array = [object valueForKey:@"objects"];
+
+    [self assert:5 equals:[array count]];
+
+    [self assert:@"one" equals:[array objectAtIndex:0]];
+    [self assert:@"two" equals:[array objectAtIndex:1]];
+    [self assert:@"three" equals:[array objectAtIndex:2]];
+    [self assert:@"four" equals:[array objectAtIndex:3]];
+    [self assert:@"five" equals:[array objectAtIndex:4]];
+
+    var indexes = [CPIndexSet indexSet];
+
+    [indexes addIndex:1];
+    [indexes addIndex:3];
+
+    [self assert:[@"two", @"four"] equals:[array objectsAtIndexes:indexes]];
+}
+
+@end