diff --git a/README.md b/README.md
index b9cc8cd3..301423ba 100644
--- a/README.md
+++ b/README.md
@@ -65,8 +65,6 @@ Picrin is a lightweight scheme implementation intended to comply with full R7RS
 
         - `(reset h)`
         - `(shift k)`
-        - `(prompt h)`
-        - `(control k)`
 
             delimited control operators
 
diff --git a/contrib/partcont/piclib/partcont.scm b/contrib/partcont/piclib/partcont.scm
index 0ced262d..4c4e3b83 100644
--- a/contrib/partcont/piclib/partcont.scm
+++ b/contrib/partcont/piclib/partcont.scm
@@ -5,26 +5,28 @@
 
   (define m #f)
 
+  (define (abort t)
+    (let ((v (t)))                      ; (t) may update m. do not place me like (m (t))
+      (m v)))
+
   (define (reset t)
-    (call/cc
-     (lambda (k)
-       (let ((n m))
+    (let ((n m))
+      (call/cc
+       (lambda (k)
          (set! m (lambda (r)
                    (set! m n)
                    (k r)))
-         (t)))))
+         (abort t)))))
 
   (define (shift h)
     (call/cc
      (lambda (k)
-       (h (lambda (v)
-            (reset (lambda ()
-                     (k v))))))))
-
-  (define prompt reset)
-  (define control shift)
+       (abort
+        (lambda ()
+          (h (lambda (v)
+               (reset (lambda ()
+                        (k v))))))))))
 
   (export shift
-          reset
-          control
-          prompt))
+          reset))
+