--- a/ClassDescription.st	Wed Nov 27 19:50:37 2019 +0100
+++ b/ClassDescription.st	Wed Nov 27 20:36:42 2019 +0100
@@ -1853,19 +1853,23 @@
             newMethod := oldMethod class trapMethodForNumArgs:(oldMethod argumentCount).
             newMethod source:code.
         ] do:[
-            Class methodRedefinitionNotification answer:#keep do:[
-                "/ hack - compilers have  different protocols... (needs fix)
-                (aCompiler respondsTo:#compile:forClass:inCategory:)
-                ifTrue:[
-                    "/ ST/X's compiler
-                    aCompiler compile:code forClass:self inCategory:cat
-                ] ifFalse:[
-                    "/ some other (TGEN) compiler
-                    aCompiler
-                            compile:code
-                            in:self
-                            notifying:nil
-                            ifFail:[].
+            UndefinedVariableError handle:[:ex |
+                ex proceed
+            ] do:[
+                Class methodRedefinitionNotification answer:#keep do:[
+                    "/ hack - compilers have  different protocols... (needs fix)
+                    (aCompiler respondsTo:#compile:forClass:inCategory:)
+                    ifTrue:[
+                        "/ ST/X's compiler
+                        aCompiler compile:code forClass:self inCategory:cat
+                    ] ifFalse:[
+                        "/ some other (TGEN) compiler
+                        aCompiler
+                                compile:code
+                                in:self
+                                notifying:nil
+                                ifFail:[].
+                    ].
                 ].
             ].
         ].