diff --git a/gc.c b/gc.c
index 9a947837..c71a2161 100644
--- a/gc.c
+++ b/gc.c
@@ -625,6 +625,17 @@ gc_mark_phase(pic_state *pic)
 
   /* library table */
   gc_mark(pic, pic->libs);
+
+  /* standard I/O ports */
+  if (pic->xSTDIN) {
+    gc_mark_object(pic, (struct pic_object *)pic->xSTDIN);
+  }
+  if (pic->xSTDOUT) {
+    gc_mark_object(pic, (struct pic_object *)pic->xSTDOUT);
+  }
+  if (pic->xSTDERR) {
+    gc_mark_object(pic, (struct pic_object *)pic->xSTDERR);
+  }
 }
 
 static void
diff --git a/include/picrin.h b/include/picrin.h
index 381b1a44..c370015e 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -108,6 +108,8 @@ typedef struct {
   struct pic_object **arena;
   size_t arena_size, arena_idx;
 
+  struct pic_port *xSTDIN, *xSTDOUT, *xSTDERR;
+
   char *native_stack_start;
 } pic_state;
 
@@ -133,7 +135,7 @@ void pic_gc_arena_restore(pic_state *, size_t);
     pic_gc_arena_restore(pic, ai);              \
   } while (0)
 
-pic_state *pic_open(int argc, char *argv[], char **envp);
+pic_state *pic_open(int argc, char *argv[], char **envp, xFILE *stdio[3]);
 void pic_close(pic_state *);
 
 void pic_define(pic_state *, const char *, pic_value); /* automatic export */
diff --git a/port.c b/port.c
index b8a15154..db1a6e96 100644
--- a/port.c
+++ b/port.c
@@ -43,8 +43,8 @@ pic_stdout(pic_state *pic)
   return pic_port_ptr(pic_apply(pic, proc, pic_nil_value()));
 }
 
-static struct pic_port *
-port_new_stdport(pic_state *pic, xFILE *file, short dir)
+struct pic_port *
+pic_port_make_stdport(pic_state *pic, xFILE *file, short dir)
 {
   struct pic_port *port;
 
@@ -690,19 +690,9 @@ pic_port_flush(pic_state *pic)
 void
 pic_init_port(pic_state *pic)
 {
-  struct pic_port *STDIN, *STDOUT, *STDERR;
-
-  STDIN = port_new_stdport(pic, xstdin, PIC_PORT_IN);
-  STDOUT = port_new_stdport(pic, xstdout, PIC_PORT_OUT);
-  STDERR = port_new_stdport(pic, xstderr, PIC_PORT_OUT);
-
-  pic_define(pic, "standard-input-port", pic_obj_value(STDIN));
-  pic_define(pic, "standard-output-port", pic_obj_value(STDOUT));
-  pic_define(pic, "standard-error-port", pic_obj_value(STDERR));
-
-  pic_define(pic, "current-input-port", pic_obj_value(pic_var_new(pic, pic_obj_value(STDIN), NULL)));
-  pic_define(pic, "current-output-port", pic_obj_value(pic_var_new(pic, pic_obj_value(STDOUT), NULL)));
-  pic_define(pic, "current-error-port", pic_obj_value(pic_var_new(pic, pic_obj_value(STDERR), NULL)));
+  pic_define(pic, "current-input-port", pic_obj_value(pic_var_new(pic, pic_obj_value(pic->xSTDIN), NULL)));
+  pic_define(pic, "current-output-port", pic_obj_value(pic_var_new(pic, pic_obj_value(pic->xSTDOUT), NULL)));
+  pic_define(pic, "current-error-port", pic_obj_value(pic_var_new(pic, pic_obj_value(pic->xSTDERR), NULL)));
 
   pic_defun(pic, "input-port?", pic_port_input_port_p);
   pic_defun(pic, "output-port?", pic_port_output_port_p);
diff --git a/state.c b/state.c
index 4810af25..28ee47e1 100644
--- a/state.c
+++ b/state.c
@@ -10,13 +10,15 @@
 #include "picrin/proc.h"
 #include "picrin/macro.h"
 #include "picrin/cont.h"
+#include "picrin/port.h"
 #include "picrin/error.h"
 
 void pic_init_core(pic_state *);
 
 pic_state *
-pic_open(int argc, char *argv[], char **envp)
+pic_open(int argc, char *argv[], char **envp, xFILE *stdio[3])
 {
+  struct pic_port *pic_port_make_stdport(pic_state *, xFILE *, short);
   char t;
 
   pic_state *pic;
@@ -72,6 +74,11 @@ pic_open(int argc, char *argv[], char **envp)
   pic->try_jmp_idx = 0;
   pic->try_jmp_size = PIC_RESCUE_SIZE;
 
+  /* standard ports */
+  pic->xSTDIN = NULL;
+  pic->xSTDOUT = NULL;
+  pic->xSTDERR = NULL;
+
   /* GC arena */
   pic->arena = calloc(PIC_ARENA_SIZE, sizeof(struct pic_object **));
   pic->arena_size = PIC_ARENA_SIZE;
@@ -148,6 +155,11 @@ pic_open(int argc, char *argv[], char **envp)
   pic->PICRIN_USER = pic_open_library(pic, pic_read_cstr(pic, "(picrin user)"));
   pic->lib = pic->PICRIN_USER;
 
+  /* standard I/O */
+  pic->xSTDIN = pic_port_make_stdport(pic, stdio[0], PIC_PORT_IN);
+  pic->xSTDOUT = pic_port_make_stdport(pic, stdio[1], PIC_PORT_OUT);
+  pic->xSTDERR = pic_port_make_stdport(pic, stdio[2], PIC_PORT_OUT);
+
   pic_init_core(pic);
 
   return pic;