--- a/ExternalStream.st	Thu Nov 24 17:55:01 2016 +0100
+++ b/ExternalStream.st	Thu Nov 24 17:55:12 2016 +0100
@@ -1932,6 +1932,12 @@
     ^ NonPositionableExternalStream makePipe.
 ! !
 
+!ExternalStream class methodsFor:'testing'!
+
+isAbstract
+    ^ self == ExternalStream
+! !
+
 !ExternalStream methodsFor:'Compatibility-Dolphin'!
 
 beText