--- a/Class.st	Wed Nov 22 23:06:32 1995 +0100
+++ b/Class.st	Thu Nov 23 01:12:39 1995 +0100
@@ -106,7 +106,7 @@
 !
 
 version
-^ '$Header: /cvs/stx/stx/libbasic/Class.st,v 1.78 1995-11-20 15:26:19 cg Exp $'! !
+^ '$Header: /cvs/stx/stx/libbasic/Class.st,v 1.79 1995-11-23 00:12:39 cg Exp $'! !
 
 !Class class methodsFor:'initialization'!
 
@@ -1917,7 +1917,9 @@
 	mySourceFileName := Smalltalk getSourceFileName:classFilename. 
 	sameFile := (fileName = mySourceFileName).
 	sameFile ifFalse:[
-	    sameFile := (fileName asFilename info at:#id) == (mySourceFileName asFilename info at:#id)
+	    mySourceFileName notNil ifTrue:[
+		sameFile := (fileName asFilename info at:#id) == (mySourceFileName asFilename info at:#id)
+	    ]
 	].
 	sameFile ifTrue:[
 	    ^ FileOutErrorSignal