diff --git a/ChangeLog b/ChangeLog
index 115f16c97..1f0e62708 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2011-03-02  Richard Frith-Macdonald <rfm@gnu.org>
+
+	* Source/NSObject.m: ([-isMemberOfClass:]) test the class returned
+	by the -class method rather than using the runtime to get the actual
+	class pointer ... fixes for when one class is pretending to be
+	another (key value observing).
+
 2011-03-01  Richard Frith-Macdonald <rfm@gnu.org>
 
 	* Source/NSKeyValueObserving.m:
diff --git a/Source/NSObject.m b/Source/NSObject.m
index b4158047c..afc0f3e38 100644
--- a/Source/NSObject.m
+++ b/Source/NSObject.m
@@ -1690,7 +1690,7 @@ objc_create_block_classes_as_subclasses_of(Class super) __attribute__((weak));
  */
 - (BOOL) isMemberOfClass: (Class)aClass
 {
-  return (object_getClass(self) == aClass) ? YES : NO;
+  return ([self class] == aClass) ? YES : NO;
 }
 
 /**