diff --git a/macro-debugger-text-lib/macro-debugger/model/yacc-ext.rkt b/macro-debugger-text-lib/macro-debugger/model/yacc-ext.rkt
index 8f51ce2..ceef3d2 100644
--- a/macro-debugger-text-lib/macro-debugger/model/yacc-ext.rkt
+++ b/macro-debugger-text-lib/macro-debugger/model/yacc-ext.rkt
@@ -19,7 +19,7 @@
   (lambda (stx)
     (raise-syntax-error #f "definitions keyword used out of context" stx)))
 
-(define-syntax (parser stx)
+(define-syntax (parser* stx)
   (syntax-case stx ()
     [(parser form ...)
      (let ([stop-list (list #'begin #'options #'productions #'definitions)]
@@ -47,3 +47,10 @@
          #'(let ()
              def ...
              (#%expression (yacc:parser opt ... (grammar prod ...))))))]))
+
+(define-syntax-rule (parser . content)
+  ;; Ensure that local expansion doesn't add
+  ;; marks due to use of a macro in the enclosing
+  ;; binding scope:
+  (let ()
+    (parser* . content)))
diff --git a/macro-debugger-text-lib/macro-debugger/util/stxobj.rkt b/macro-debugger-text-lib/macro-debugger/util/stxobj.rkt
index 95d7aad..c3c3a10 100644
--- a/macro-debugger-text-lib/macro-debugger/util/stxobj.rkt
+++ b/macro-debugger-text-lib/macro-debugger/util/stxobj.rkt
@@ -1,32 +1,8 @@
 #lang racket/base
-(require (rename-in racket/contract/base [-> c:->])
-         ffi/unsafe)
 
-(define lib (ffi-lib #f))
+(provide get-marks)
 
-(define get-marks
-  (get-ffi-obj "scheme_stx_extract_marks" lib
-               (_fun _scheme -> _scheme)))
-
-#|
-(define (simplify-marks marklist)
-  (simplify* (sort marklist <)))
-
-(define (simplify* marklist)
-  (cond [(null? marklist) marklist]
-        [(null? (cdr marklist)) marklist]
-        [(= (car marklist) (cadr marklist))
-         (simplify* (cddr marklist))]
-        [else
-         (let ([result (simplify* (cdr marklist))])
-           (if (eq? result (cdr marklist))
-               marklist
-               (cons (car marklist) result)))]))
-
-(provide simplify-marks)
-|#
-
-(provide/contract
- [get-marks
-  ;; syntax? check needed for safety!
-  (c:-> syntax? any)])
+(define (get-marks stx)
+  (define info (syntax-debug-info stx))
+  (for ([e (in-list (hash-ref info 'context))])
+    (vector-ref e 0)))