diff --git a/Objective-J/Debug.js b/Objective-J/Debug.js
index b22493dc0..c0102193d 100644
--- a/Objective-J/Debug.js
+++ b/Objective-J/Debug.js
@@ -58,6 +58,17 @@ GLOBAL(objj_msgSend_reset) = function()
     objj_msgSendFast1 = objj_msgSendFast1_original;
     objj_msgSendFast2 = objj_msgSendFast2_original;
     objj_msgSendFast3 = objj_msgSendFast3_original;
+
+    objj_enumerateClassesUsingBlock(function(aClass) {
+        if (aClass.hasOwnProperty("objj_msgSend"))
+        {
+            aClass.objj_msgSend = objj_msgSendFast;
+            aClass.objj_msgSend0 = objj_msgSendFast0;
+            aClass.objj_msgSend1 = objj_msgSendFast1;
+            aClass.objj_msgSend2 = objj_msgSendFast2;
+            aClass.objj_msgSend3 = objj_msgSendFast3;
+        }
+    });
 }
 
 // decorate both objj_msgSend and objj_msgSendSuper
diff --git a/Tests/Objective-J/DebugTest.j b/Tests/Objective-J/DebugTest.j
new file mode 100644
index 000000000..d48daa5fb
--- /dev/null
+++ b/Tests/Objective-J/DebugTest.j
@@ -0,0 +1,72 @@
+var SEEN_MESSAGES = [];
+
+objj_test_decorator = function(msgSend)
+{
+    return function(aReceiverOrSuper, aSelector)
+    {
+        if (aSelector === @selector(intify:))
+            SEEN_MESSAGES.push([aReceiverOrSuper, aSelector]);
+        return msgSend.apply(this, arguments);
+    };
+}
+
+@implementation TestClass0 : CPObject
+
+- (CPInteger)intify:(CPInteger)anInput
+{
+    return anInput * 2; // now twice as int
+}
+
+@end
+
+@implementation TestClass1 : CPObject
+
+- (CPInteger)intify:(CPInteger)anInput
+{
+    return anInput * 2; // now twice as int
+}
+
+@end
+
+
+@implementation DebugTest : OJTestCase
+
+- (void)setUp
+{
+    SEEN_MESSAGES = [];
+}
+
+- (void)tearDown
+{
+    objj_msgSend_reset();
+}
+
+- (void)test_objj_msgSend_decorate_should_replace_fast_msgSend_for_unitialised_class
+{
+    objj_msgSend_decorate(objj_test_decorator);
+    var a = [TestClass0 new];
+    [self assert:[a intify:3] equals:6];
+    [self assert:SEEN_MESSAGES equals:[[a, @selector(intify:)]]];
+}
+
+- (void)test_objj_msgSend_decorate_should_replace_fast_msgSend_for_initialised_class
+{
+    var a = [TestClass1 new];
+    [a intify:5];
+
+    objj_msgSend_decorate(objj_test_decorator);
+    [self assert:[a intify:3] equals:6];
+    [self assert:SEEN_MESSAGES equals:[[a, @selector(intify:)]]];
+}
+
+- (void)test_objj_msgSend_reset_should_reset
+{
+    objj_msgSend_decorate(objj_test_decorator);
+    var a = [TestClass1 new];
+    [self assert:[a intify:3] equals:6];
+    objj_msgSend_reset();
+    [self assert:[a intify:3] equals:6];
+    [self assert:SEEN_MESSAGES equals:[[a, @selector(intify:)]]];
+}
+
+@end