diff --git a/mrbgems/mruby-io/src/io.c b/mrbgems/mruby-io/src/io.c
index 3cfe7efbc..70d48a01e 100644
--- a/mrbgems/mruby-io/src/io.c
+++ b/mrbgems/mruby-io/src/io.c
@@ -71,12 +71,11 @@ static void mrb_io_free(mrb_state *mrb, void *ptr);
 struct mrb_data_type mrb_io_type = { "IO", mrb_io_free };
 
 
-static struct mrb_io *io_get_open_fptr(mrb_state *mrb, mrb_value self);
 static int mrb_io_modestr_to_flags(mrb_state *mrb, const char *modestr);
 static int mrb_io_mode_to_flags(mrb_state *mrb, mrb_value mode);
 static void fptr_finalize(mrb_state *mrb, struct mrb_io *fptr, int quiet);
 
-static struct mrb_io *
+static struct mrb_io*
 io_get_open_fptr(mrb_state *mrb, mrb_value self)
 {
   struct mrb_io *fptr;
@@ -796,16 +795,33 @@ fptr_finalize(mrb_state *mrb, struct mrb_io *fptr, int quiet)
   }
 }
 
+static struct mrb_io*
+io_get_read_fptr(mrb_state *mrb, mrb_value self)
+{
+  struct mrb_io *fptr = io_get_open_fptr(mrb, self);
+  if (!fptr->readable) {
+    mrb_raise(mrb, E_IO_ERROR, "not opened for reading");
+  }
+  return fptr;
+}
+
 static mrb_value
 mrb_io_check_readable(mrb_state *mrb, mrb_value self)
 {
-  struct mrb_io *fptr = io_get_open_fptr(mrb, self);
-  if (! fptr->readable) {
-    mrb_raise(mrb, E_IO_ERROR, "not opened for reading");
-  }
+  io_get_read_fptr(mrb, self);
   return mrb_nil_value();
 }
 
+static struct mrb_io*
+io_get_write_fptr(mrb_state *mrb, mrb_value self)
+{
+  struct mrb_io *fptr = io_get_open_fptr(mrb, self);
+  if (!fptr->writable) {
+    mrb_raise(mrb, E_IO_ERROR, "not opened for writing");
+  }
+  return fptr;
+}
+
 static mrb_value
 mrb_io_isatty(mrb_state *mrb, mrb_value self)
 {
@@ -944,10 +960,7 @@ mrb_io_sysread_common(mrb_state *mrb,
     mrb_str_modify(mrb, RSTRING(buf));
   }
 
-  fptr = io_get_open_fptr(mrb, io);
-  if (!fptr->readable) {
-    mrb_raise(mrb, E_IO_ERROR, "not opened for reading");
-  }
+  fptr = io_get_read_fptr(mrb, io);
   ret = readfunc(fptr->fd, RSTRING_PTR(buf), (fsize_t)maxlen, offset);
   if (ret < 0) {
     mrb_sys_fail(mrb, "sysread failed");
@@ -997,11 +1010,7 @@ mrb_io_syswrite_common(mrb_state *mrb,
   struct mrb_io *fptr;
   int fd, length;
 
-  fptr = io_get_open_fptr(mrb, io);
-  if (! fptr->writable) {
-    mrb_raise(mrb, E_IO_ERROR, "not opened for writing");
-  }
-
+  fptr = io_get_write_fptr(mrb, io);
   if (fptr->fd2 == -1) {
     fd = fptr->fd;
   } else {
@@ -1502,12 +1511,8 @@ mrb_io_readchar(mrb_state *mrb, mrb_value self)
     if (len == 1 && RSTRING_LEN(buf) < 4) { /* partial UTF-8 */
       mrb_int blen = RSTRING_LEN(buf);
       ssize_t n;
+      struct mrb_io *fptr = io_get_read_fptr(mrb, self);
 
-      struct mrb_io *fptr = io_get_open_fptr(mrb, self);
-
-      if (!fptr->readable) {
-        mrb_raise(mrb, E_IO_ERROR, "not opened for reading");
-      }
       /* refill the buffer */
       mrb_str_resize(mrb, buf, 4096);
       n = read(fptr->fd, RSTRING_PTR(buf)+blen, 4096-blen);