--- a/PositionableStream.st	Thu Nov 24 16:16:04 2016 +0100
+++ b/PositionableStream.st	Thu Nov 24 16:16:15 2016 +0100
@@ -123,6 +123,12 @@
     "Modified: / 13-07-2006 / 20:36:54 / cg"
 ! !
 
+!PositionableStream class methodsFor:'testing'!
+
+isAbstract
+    ^ self == PositionableStream
+! !
+
 !PositionableStream methodsFor:'Compatibility-Dolphin'!
 
 endChunk