--- a/CharacterEncoderImplementations__SingleByteEncoder.st	Sun Jan 29 11:04:01 2017 +0000
+++ b/CharacterEncoderImplementations__SingleByteEncoder.st	Wed Feb 01 11:28:48 2017 +0000
@@ -47,6 +47,14 @@
 
 !SingleByteEncoder class methodsFor:'queries'!
 
+isAbstract
+    "Return if this class is an abstract class.
+     True is returned here; false for subclasses.
+     Abstract subclasses must redefine this again."
+
+    ^ self == CharacterEncoderImplementations::SingleByteEncoder
+!
+
 maxCode
     ^ 255 
 !