diff --git a/Foundation/CPArray/CPMutableArray.j b/Foundation/CPArray/CPMutableArray.j
index ec4a7769c..3815919e2 100644
--- a/Foundation/CPArray/CPMutableArray.j
+++ b/Foundation/CPArray/CPMutableArray.j
@@ -530,7 +530,7 @@ var sortArrayUsingJSDescriptors = function(a, d)
                     if (value1 === nil || value1 === cpNull)
                         o = value2 === nil || value2 === cpNull ? CPOrderedSame : CPOrderedAscending;
                     else
-                        o = value2 === nil || value2 === cpNull ? CPOrderedDescending : objj_msgSend(value1, dd.s, value2);
+                        o = value2 === nil || value2 === cpNull ? CPOrderedDescending : value1.isa.objj_msgSend1(value1, dd.s, value2);
 
                     if (o && !dd.a)
                         o = -o;
diff --git a/Foundation/CPArray/_CPArray.j b/Foundation/CPArray/_CPArray.j
index 093023904..ba2e0cd9f 100755
--- a/Foundation/CPArray/_CPArray.j
+++ b/Foundation/CPArray/_CPArray.j
@@ -608,9 +608,11 @@ var concat = Array.prototype.concat,
         }
     }
 
-    else
+    else {
+        var anIsa = self.isa;
         for (; index < count; ++index)
-            objj_msgSend([self objectAtIndex:index], aSelector);
+            anIsa.objj_msgSend0([self objectAtIndex:index], aSelector);
+    }
 }
 
 - (void)enumerateObjectsUsingBlock:(Function /*(id anObject, int idx, @ref BOOL stop)*/)aFunction
@@ -748,7 +750,7 @@ var concat = Array.prototype.concat,
     // passed in is an array, we end up with its contents added instead of itself.
     push.call(argumentArray, anObject);
 
-    return objj_msgSend([self class], @selector(arrayWithArray:), argumentArray);
+    return [[self class] arrayWithArray:argumentArray];
 }
 
 /*!
@@ -763,7 +765,7 @@ var concat = Array.prototype.concat,
     var anArray = anArray.isa === _CPJavaScriptArray ? anArray : [anArray _javaScriptArrayCopy],
         argumentArray = concat.call([self _javaScriptArrayCopy], anArray);
 
-    return objj_msgSend([self class], @selector(arrayWithArray:), argumentArray);
+    return [[self class] arrayWithArray:argumentArray];
 }
 
 /*
@@ -801,7 +803,7 @@ var concat = Array.prototype.concat,
     for (; index < count; ++index)
         push.call(argumentArray, [self objectAtIndex:index]);
 
-    return objj_msgSend([self class], @selector(arrayWithArray:), argumentArray);
+    return [[self class] arrayWithArray:argumentArray];
 }
 
 // Sorting arrays
diff --git a/Foundation/CPArray/_CPJavaScriptArray.j b/Foundation/CPArray/_CPJavaScriptArray.j
index c3765ad2e..5589e75b0 100644
--- a/Foundation/CPArray/_CPJavaScriptArray.j
+++ b/Foundation/CPArray/_CPJavaScriptArray.j
@@ -196,8 +196,10 @@ var concat = Array.prototype.concat,
     }
 
     else
-        for (; index < count; ++index)
-            objj_msgSend(self[index], aSelector);
+        for (; index < count; ++index) {
+            var receiver = self[index];
+            receiver == nil ? nil : receiver.isa.objj_msgSend0(receiver, aSelector);
+        }
 }
 
 - (CPArray)arrayByAddingObject:(id)anObject
diff --git a/Foundation/CPKeyValueCoding.j b/Foundation/CPKeyValueCoding.j
index fa86c5f9c..b67d78b88 100644
--- a/Foundation/CPKeyValueCoding.j
+++ b/Foundation/CPKeyValueCoding.j
@@ -108,7 +108,7 @@ var CPObjectAccessorsForClassKey = @"$CPObjectAccessorsForClassKey",
     switch (accessor[0])
     {
         case 0:
-            return objj_msgSend(self, accessor[1]);
+            return self.isa.objj_msgSend0(self, accessor[1]);
 
         case 1:
             // FIXME: We shouldn't be creating a new one every time.
@@ -226,7 +226,7 @@ var CPObjectAccessorsForClassKey = @"$CPObjectAccessorsForClassKey",
 
     switch (modifier[0])
     {
-        case 0:     return objj_msgSend(self, modifier[1], aValue);
+        case 0:     return self.isa.objj_msgSend1(self, modifier[1], aValue);
 
         case 1:     if ([theClass accessInstanceVariablesDirectly])
                     {
@@ -341,21 +341,21 @@ var CPObjectAccessorsForClassKey = @"$CPObjectAccessorsForClassKey",
 
 - (CPUInteger)count
 {
-    return objj_msgSend(_target, _countOfSelector);
+    return _target == nil ? nil : _target.isa.objj_msgSend0(_target, _countOfSelector);
 }
 
 - (id)objectAtIndex:(CPUInteger)anIndex
 {
     if (_objectInAtIndexSelector)
-        return objj_msgSend(_target, _objectInAtIndexSelector, anIndex);
+        return _target == nil ? nil : _target.isa.objj_msgSend1(_target, _objectInAtIndexSelector, anIndex);
 
-    return objj_msgSend(_target, _atIndexesSelector, [CPIndexSet indexSetWithIndex:anIndex])[0];
+    return _target == nil ? nil : _target.isa.objj_msgSend1(_target, _atIndexesSelector, [CPIndexSet indexSetWithIndex:anIndex])[0];
 }
 
 - (CPArray)objectsAtIndexes:(CPIndexSet)indexes
 {
     if (_atIndexesSelector)
-        return objj_msgSend(_target, _atIndexesSelector, indexes);
+        return _target == nil ? nil : _target.isa.objj_msgSend1(_target, _atIndexesSelector, indexes);
 
     return [super objectsAtIndexes:indexes];
 }
@@ -408,17 +408,17 @@ var CPObjectAccessorsForClassKey = @"$CPObjectAccessorsForClassKey",
 
 - (CPUInteger)count
 {
-    return objj_msgSend(_target, _countOfSelector);
+    return _target == nil ? nil : _target.isa.objj_msgSend0(_target, _countOfSelector);
 }
 
 - (CPEnumerator)objectEnumerator
 {
-    return objj_msgSend(_target, _enumeratorOfSelector);
+    return _target == nil ? nil : _target.isa.objj_msgSend0(_target, _enumeratorOfSelector);
 }
 
 - (id)member:(id)anObject
 {
-    return objj_msgSend(_target, _memberOfSelector, anObject);
+    return _target == nil ? nil : _target.isa.objj_msgSend1(_target, _memberOfSelector, anObject);
 }
 
 - (Class)classForCoder
diff --git a/Foundation/CPObject.j b/Foundation/CPObject.j
index ae5a39ac1..912aafa09 100644
--- a/Foundation/CPObject.j
+++ b/Foundation/CPObject.j
@@ -364,7 +364,7 @@ CPLog(@"Got some class: %@", inst);
 */
 - (id)performSelector:(SEL)aSelector
 {
-    return objj_msgSend(self, aSelector);
+    return self.isa.objj_msgSend0(self, aSelector);
 }
 
 /*!
@@ -375,7 +375,7 @@ CPLog(@"Got some class: %@", inst);
 */
 - (id)performSelector:(SEL)aSelector withObject:(id)anObject
 {
-    return objj_msgSend(self, aSelector, anObject);
+    return self.isa.objj_msgSend1(self, aSelector, anObject);
 }
 
 /*!
@@ -387,7 +387,7 @@ CPLog(@"Got some class: %@", inst);
 */
 - (id)performSelector:(SEL)aSelector withObject:(id)anObject withObject:(id)anotherObject
 {
-    return objj_msgSend(self, aSelector, anObject, anotherObject);
+    return self.isa.objj_msgSend2(self, aSelector, anObject, anotherObject);
 }
 
 /*!
diff --git a/Foundation/CPProxy.j b/Foundation/CPProxy.j
index ceeac578d..2234a6f39 100644
--- a/Foundation/CPProxy.j
+++ b/Foundation/CPProxy.j
@@ -106,17 +106,17 @@
 
 - (id)performSelector:(SEL)aSelector
 {
-    return objj_msgSend(self, aSelector);
+    return self.isa.objj_msgSend0(self, aSelector);
 }
 
 - (id)performSelector:(SEL)aSelector withObject:(id)anObject
 {
-    return objj_msgSend(self, aSelector, anObject);
+    return self.isa.objj_msgSend1(self, aSelector, anObject);
 }
 
 - (id)performSelector:(SEL)aSelector withObject:(id)anObject withObject:(id)anotherObject
 {
-    return objj_msgSend(self, aSelector, anObject, anotherObject);
+    return self.isa.objj_msgSend2(self, aSelector, anObject, anotherObject);
 }
 
 - (BOOL)isProxy
diff --git a/Objective-J/Runtime.js b/Objective-J/Runtime.js
index 4eb12cae8..75a43bf78 100644
--- a/Objective-J/Runtime.js
+++ b/Objective-J/Runtime.js
@@ -466,7 +466,7 @@ var _class_initialize = function(/*Class*/ aClass)
         meta.objj_msgSend2 = objj_msgSendFast2;
         meta.objj_msgSend3 = objj_msgSendFast3;
 
-        objj_msgSend(aClass, "initialize");
+        meta.objj_msgSend0(aClass, "initialize");
 
         CHANGEINFO(meta, CLS_INITIALIZED, CLS_INITIALIZING);
     }
@@ -505,16 +505,20 @@ var _objj_forward = function(self, _cmd)
 
                 if (invocationClass)
                 {
-                    var invocation = objj_msgSend(invocationClass, SEL_invocationWithMethodSignature_, signature),
+                    var invocation = invocationClass.isa.objj_msgSend1(invocationClass, SEL_invocationWithMethodSignature_, signature),
                         index = 0,
                         count = arguments.length;
 
-                    for (; index < count; ++index)
-                        objj_msgSend(invocation, SEL_setArgument_atIndex_, arguments[index], index);
+                    if (invocation != null) {
+                        var invocationIsa = invocation.isa;
+
+                        for (; index < count; ++index)
+                            invocationIsa.objj_msgSend2(invocation, SEL_setArgument_atIndex_, arguments[index], index);
+                    }
 
                     forwardInvocationImplementation.method_imp.call(this, self, SEL_forwardInvocation_, invocation);
 
-                    return objj_msgSend(invocation, SEL_returnValue);
+                    return invocation == null ? null : invocationIsa.objj_msgSend0(invocation, SEL_returnValue);
                 }
             }
         }
@@ -1000,7 +1004,7 @@ objj_class.prototype.toString = objj_object.prototype.toString = function()
     var isa = this.isa;
 
     if (class_getInstanceMethod(isa, SEL_description))
-        return objj_msgSend(this, SEL_description);
+        return isa.objj_msgSend0(this, SEL_description);
 
     if (class_isMetaClass(isa))
         return this.name;