--- a/ParserFlags.st	Wed Oct 31 17:03:04 2012 +0100
+++ b/ParserFlags.st	Wed Oct 31 17:14:32 2012 +0100
@@ -1493,7 +1493,9 @@
 
     topDir := topDirArg.
     OperatingSystem isMSWINDOWSlike ifTrue:[
-        topDir := topDirArg copyReplaceAll:$/ with:$\.
+        topDirArg isString ifTrue:[
+            topDir := topDirArg copyReplaceAll:$/ with:$\.
+        ]
     ].
 
     "/ if in the development directory, use ./modules
@@ -2475,11 +2477,11 @@
 !ParserFlags class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libcomp/ParserFlags.st,v 1.94 2012-10-31 16:03:04 cg Exp $'
+    ^ '$Header: /cvs/stx/stx/libcomp/ParserFlags.st,v 1.95 2012-10-31 16:14:32 cg Exp $'
 !
 
 version_CVS
-    ^ '$Header: /cvs/stx/stx/libcomp/ParserFlags.st,v 1.94 2012-10-31 16:03:04 cg Exp $'
+    ^ '$Header: /cvs/stx/stx/libcomp/ParserFlags.st,v 1.95 2012-10-31 16:14:32 cg Exp $'
 ! !
 
 ParserFlags initialize!