diff --git a/Source/NSCountedSet.m b/Source/NSCountedSet.m
index b56d1aef1..ab275c5cc 100644
--- a/Source/NSCountedSet.m
+++ b/Source/NSCountedSet.m
@@ -115,13 +115,13 @@ static Class NSCountedSet_concrete_class;
 
 - initWithCoder: aCoder
 {
-  [self notImplemented:_cmd];
-  return self;
+  [self subclassResponsibility:_cmd];
+  return nil;
 }
 
 - (void) encodeWithCoder: aCoder
 {
-  [self notImplemented:_cmd];
+  [self subclassResponsibility:_cmd];
 }
 
 @end