diff --git a/collects/macro-debugger/view/interfaces.ss b/collects/macro-debugger/view/interfaces.ss
index ed114cf..b8ad2a5 100644
--- a/collects/macro-debugger/view/interfaces.ss
+++ b/collects/macro-debugger/view/interfaces.ss
@@ -27,10 +27,12 @@
      pref:identifier=?
      pref:show-rename-steps?
      pref:highlight-foci?
+     pref:highlight-frontier?
      pref:suppress-warnings?
      pref:one-by-one?
      pref:extra-navigation?
      pref:debug-catch-errors?
+     pref:force-letrec-transformation?
      ))
 
   ;; macro-stepper-config%
diff --git a/collects/macro-debugger/view/prefs.ss b/collects/macro-debugger/view/prefs.ss
index a6d5115..1c642db 100644
--- a/collects/macro-debugger/view/prefs.ss
+++ b/collects/macro-debugger/view/prefs.ss
@@ -13,27 +13,29 @@
            [() (preferences:get 'prop)]
            [(newval) (preferences:set 'prop newval)]))]))
 
+  (preferences:set-default 'MacroStepper:Frame:Width 700 number?)
+  (preferences:set-default 'MacroStepper:Frame:Height 600 number?)
+  (preferences:set-default 'MacroStepper:PropertiesPanelPercentage 1/3 number?)
+  (preferences:set-default 'MacroStepper:MacroHiding? #t boolean?)
+  (preferences:set-default 'MacroStepper:ShowSyntaxProperties? #f boolean?)
+  (preferences:set-default 'MacroStepper:ShowHidingPanel? #t boolean?)
+  (preferences:set-default 'MacroStepper:HidePrimitives? #t boolean?)
+  (preferences:set-default 'MacroStepper:HideLibs? #t boolean?)
+  (preferences:set-default 'MacroStepper:IdentifierComparison "bound-identifier=?" string?)
+  (preferences:set-default 'MacroStepper:HighlightFoci? #t boolean?)
+  (preferences:set-default 'MacroStepper:HighlightFrontier? #t boolean?)
+  (preferences:set-default 'MacroStepper:ShowRenameSteps? #f boolean?)
+  (preferences:set-default 'MacroStepper:SuppressWarnings? #f boolean?)
+  (preferences:set-default 'MacroStepper:OneByOne? #f boolean?)
+  (preferences:set-default 'MacroStepper:ExtraNavigation? #f boolean?)
+  (preferences:set-default 'MacroStepper:DebugCatchErrors? #t boolean?)
+  (preferences:set-default 'MacroStepper:ForceLetrecTransformation? #f boolean?)
+
   (define prefs@
     (unit
       (import)
       (export prefs^)
       
-      (preferences:set-default 'MacroStepper:Frame:Width 700 number?)
-      (preferences:set-default 'MacroStepper:Frame:Height 600 number?)
-      (preferences:set-default 'MacroStepper:PropertiesPanelPercentage 1/3 number?)
-      (preferences:set-default 'MacroStepper:MacroHiding? #t boolean?)
-      (preferences:set-default 'MacroStepper:ShowSyntaxProperties? #f boolean?)
-      (preferences:set-default 'MacroStepper:ShowHidingPanel? #t boolean?)
-      (preferences:set-default 'MacroStepper:HidePrimitives? #t boolean?)
-      (preferences:set-default 'MacroStepper:HideLibs? #t boolean?)
-      (preferences:set-default 'MacroStepper:IdentifierComparison "bound-identifier=?" string?)
-      (preferences:set-default 'MacroStepper:HighlightFoci? #t boolean?)
-      (preferences:set-default 'MacroStepper:ShowRenameSteps? #f boolean?)
-      (preferences:set-default 'MacroStepper:SuppressWarnings? #f boolean?)
-      (preferences:set-default 'MacroStepper:OneByOne? #f boolean?)
-      (preferences:set-default 'MacroStepper:ExtraNavigation? #f boolean?)
-      (preferences:set-default 'MacroStepper:DebugCatchErrors? #t boolean?)
-      
       (pref:get/set pref:width MacroStepper:Frame:Width)
       (pref:get/set pref:height MacroStepper:Frame:Height)
       (pref:get/set pref:props-percentage MacroStepper:PropertiesPanelPercentage)
@@ -44,11 +46,13 @@
       (pref:get/set pref:hide-libs? MacroStepper:HideLibs?)
       (pref:get/set pref:identifier=? MacroStepper:IdentifierComparison)
       (pref:get/set pref:highlight-foci? MacroStepper:HighlightFoci?)
+      (pref:get/set pref:highlight-frontier? MacroStepper:HighlightFrontier?)
       (pref:get/set pref:show-rename-steps? MacroStepper:ShowRenameSteps?)
       (pref:get/set pref:suppress-warnings? MacroStepper:SuppressWarnings?)
       (pref:get/set pref:one-by-one? MacroStepper:OneByOne?)
       (pref:get/set pref:extra-navigation? MacroStepper:ExtraNavigation?)
       (pref:get/set pref:debug-catch-errors? MacroStepper:DebugCatchErrors?)
+      (pref:get/set pref:force-letrec-transformation? MacroStepper:ForceLetrecTransformation?)
       
       ))
   )