diff --git a/piclib/CMakeLists.txt b/piclib/CMakeLists.txt
index ce373fb2..50b59f9b 100644
--- a/piclib/CMakeLists.txt
+++ b/piclib/CMakeLists.txt
@@ -1,5 +1,5 @@
 list(APPEND PICLIB_SCHEME_LIBS
-  ${PROJECT_SOURCE_DIR}/piclib/picrin/macro.scm
+  ${PROJECT_SOURCE_DIR}/piclib/picrin/macro.scm # the only dependency prelude requires
   ${PROJECT_SOURCE_DIR}/piclib/prelude.scm
   ${PROJECT_SOURCE_DIR}/piclib/picrin/array.scm
   ${PROJECT_SOURCE_DIR}/piclib/picrin/dictionary.scm
diff --git a/piclib/prelude.scm b/piclib/prelude.scm
index 6d8d6be9..7b45efa5 100644
--- a/piclib/prelude.scm
+++ b/piclib/prelude.scm
@@ -329,18 +329,6 @@
        expr)
       (reverse list)))
 
-  (define (predefine var)
-    `(define ,var #f))
-
-  (define (predefines vars)
-    (map predefine vars))
-
-  (define (assign var val)
-    `(set! ,var ,val))
-
-  (define (assigns vars vals)
-    (map assign vars vals))
-
   (define uniq
     (let ((counter 0))
       (lambda (x)
@@ -355,10 +343,15 @@
               (formal* (walk uniq formal))
               (exprs   (cddr form)))
          `(begin
-            ,@(predefines (flatten formal))
+            ,@(map
+               (lambda (var) `(define ,var #f))
+               (flatten formal))
             (call-with-values (lambda () ,@exprs)
               (lambda ,formal*
-                ,@(assigns (flatten formal) (flatten formal*)))))))))
+                ,@(map
+                   (lambda (var val) `(set! ,var ,val))
+                   (flatten formal)
+                   (flatten formal*)))))))))
 
   (export let-values
           let*-values