--- a/ExternalStructure.st	Sun Apr 03 07:04:52 2016 +0200
+++ b/ExternalStructure.st	Fri Apr 08 07:02:36 2016 +0100
@@ -157,6 +157,12 @@
         size:(anExternalAddressOrExternalStructure size).
 ! !
 
+!ExternalStructure methodsFor:'testing'!
+
+isExternalStructure
+    ^ true
+! !
+
 !ExternalStructure class methodsFor:'documentation'!
 
 version