diff --git a/Foundation/CPArray/_CPJavaScriptArray.j b/Foundation/CPArray/_CPJavaScriptArray.j
index 640a9bdf0..6785d8b14 100644
--- a/Foundation/CPArray/_CPJavaScriptArray.j
+++ b/Foundation/CPArray/_CPJavaScriptArray.j
@@ -35,12 +35,12 @@ var indexOf = Array.prototype.indexOf,
 
 - (id)initWithArray:(CPArray)anArray
 {
-    return slice.call(anArray, 0);
+    return [self initWithArray:anArray copyItems:NO];
 }
 
 - (id)initWithArray:(CPArray)anArray copyItems:(BOOL)shouldCopyItems
 {
-    if (!shouldCopyItems)
+    if (!shouldCopyItems && anArray.isa === _CPJavaScriptArray)
         return slice.call(anArray, 0);
 
     self = [super init];
diff --git a/Foundation/CPKeyValueCoding.j b/Foundation/CPKeyValueCoding.j
index c618e6d73..5bba5ffbf 100644
--- a/Foundation/CPKeyValueCoding.j
+++ b/Foundation/CPKeyValueCoding.j
@@ -347,8 +347,8 @@ var CPObjectAccessorsForClassKey            = @"$CPObjectAccessorsForClassKey",
 
 - (id)copy
 {
-    var objects = [self objectsAtIndexes:[CPIndexSet indexSetWithIndexesInRange:CPMakeRange(0, [self count])]];
-    return [[CPArray alloc] initWithArray:objects];
+    // We do this to ensure we return a CPArray.
+    return [CPArray arrayWithArray:self];
 }
 
 @end
@@ -408,14 +408,8 @@ var CPObjectAccessorsForClassKey            = @"$CPObjectAccessorsForClassKey",
 
 - (id)copy
 {
-    var objects = [],
-        object = nil,
-        objectEnumerator = [self objectEnumerator];
-
-    while ((object = [objectEnumerator nextObject]) !== nil)
-            objects.push(object);
-
-    return [[CPSet alloc] initWithArray:objects];
+    // We do this to ensure we return a CPSet.
+    return [CPSet setWithSet:self];
 }
 
 @end
diff --git a/Foundation/CPSet/CPSet.j b/Foundation/CPSet/CPSet.j
index db19b8d56..1ae1fa5bc 100644
--- a/Foundation/CPSet/CPSet.j
+++ b/Foundation/CPSet/CPSet.j
@@ -383,7 +383,7 @@
 
 - (id)copy
 {
-    return [[CPSet alloc] initWithSet:self];
+    return [[self class] setWithSet:self];
 }
 
 - (id)mutableCopy