Index: Source/NSWindowController.m
===================================================================
--- Source/NSWindowController.m	(revision 26980)
+++ Source/NSWindowController.m	(working copy)
@@ -502,7 +502,15 @@
   // be empty, just to conform to NSCoding, so we do an -init on
   // unarchival.  ?
 
-  [super encodeWithCoder: coder];
+  if ([NSWindowController version] >= 1)
+    {
+      [super encodeWithCoder: coder];
+    }
+  else
+    {
+      /* backward compatibility: old NSWindowController instances are not
+         subclasses of NSResponder, but of NSObject, so do nothing here */
+    }
 }
 
 @end