diff --git a/include/picrin/config.h b/include/picrin/config.h
index 79b8fc3c..5291a927 100644
--- a/include/picrin/config.h
+++ b/include/picrin/config.h
@@ -2,18 +2,12 @@
  * See Copyright Notice in picrin.h
  */
 
-/** contribution libraries */
-/* #define PIC_CONTRIB_INITS */
-
 /** switch normal VM and direct threaded VM */
 /* #define PIC_DIRECT_THREADED_VM 1 */
 
 /** switch internal value representation */
 /* #define PIC_NAN_BOXING 1 */
 
-/** enable readline module */
-/* #define PIC_ENABLE_READLINE 1 */
-
 /** treat false value as none */
 /* #define PIC_NONE_IS_FALSE 1 */
 
@@ -47,10 +41,6 @@
 # error please activate c99 features
 #endif
 
-#ifndef PIC_CONTRIB_INITS
-# define PIC_CONTRIB_INITS
-#endif
-
 #ifndef PIC_DIRECT_THREADED_VM
 # if defined(__GNUC__) || defined(__CLANG__)
 #  define PIC_DIRECT_THREADED_VM 1
@@ -63,14 +53,6 @@
 # endif
 #endif
 
-#ifndef PIC_ENABLE_READLINE
-# if PIC_READLINE_FOUND
-#  define PIC_ENABLE_READLINE 1
-# else
-#  define PIC_ENABLE_READLINE 0
-# endif
-#endif
-
 #ifndef PIC_NONE_IS_FALSE
 # define PIC_NONE_IS_FALSE 1
 #endif