diff --git a/mrbgems/mruby-io/mrblib/io.rb b/mrbgems/mruby-io/mrblib/io.rb
index b7aba6498..175ecbb0c 100644
--- a/mrbgems/mruby-io/mrblib/io.rb
+++ b/mrbgems/mruby-io/mrblib/io.rb
@@ -115,14 +115,6 @@ class IO
     end
   end
 
-  def getc
-    begin
-      readchar
-    rescue EOFError
-      nil
-    end
-  end
-
   def getbyte
     readbyte
   rescue EOFError
diff --git a/mrbgems/mruby-io/src/io.c b/mrbgems/mruby-io/src/io.c
index 6a6cf13b6..1abdffc5b 100644
--- a/mrbgems/mruby-io/src/io.c
+++ b/mrbgems/mruby-io/src/io.c
@@ -1796,31 +1796,22 @@ io_readline(mrb_state *mrb, mrb_value io)
 }
 
 static mrb_value
-io_readchar(mrb_state *mrb, mrb_value io)
+io_getc(mrb_state *mrb, mrb_value io)
 {
   mrb_value buf;
   mrb_int len = 1;
-#ifdef MRB_UTF8_STRING
-  unsigned char c;
-#endif
+  struct mrb_io *fptr = io_get_read_fptr(mrb, io);
 
-  mrb->c->ci->mid = 0;
-  io_read_buf(mrb, io);
+  io_read_buf_noraise(mrb, io);
   buf = io_buf(mrb, io);
+  if (fptr->eof) return mrb_nil_value();
 #ifdef MRB_UTF8_STRING
-  c = RSTRING_PTR(buf)[0];
+  unsigned char c = RSTRING_PTR(buf)[0];
   if (c & 0x80) {
     len = mrb_utf8len(RSTRING_PTR(buf), RSTRING_END(buf));
     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, io);
-
-      /* refill the buffer */
-      mrb_str_resize(mrb, buf, 4096);
-      n = read(fptr->fd, RSTRING_PTR(buf)+blen, 4096-blen);
-      if (n < 0) mrb_sys_fail(mrb, "sysread failed");
-      mrb_str_resize(mrb, buf, blen+n);
+      io_read_buf_noraise(mrb, io);
+      buf = io_buf(mrb, io);
       len = mrb_utf8len(RSTRING_PTR(buf), RSTRING_END(buf));
     }
   }
@@ -1828,6 +1819,16 @@ io_readchar(mrb_state *mrb, mrb_value io)
   return io_bufread(mrb, buf, len);
 }
 
+static mrb_value
+io_readchar(mrb_state *mrb, mrb_value io)
+{
+  mrb_value result = io_getc(mrb, io);
+  if (mrb_nil_p(result)) {
+    eof_error(mrb);
+  }
+  return result;
+}
+
 static mrb_value
 io_readbyte(mrb_state *mrb, mrb_value io)
 {
@@ -1868,7 +1869,9 @@ mrb_init_io(mrb_state *mrb)
   mrb_define_method(mrb, io, "initialize_copy", io_init_copy, MRB_ARGS_REQ(1));
   mrb_define_method(mrb, io, "isatty",     io_isatty,     MRB_ARGS_NONE());
   mrb_define_method(mrb, io, "eof?",       io_eof,        MRB_ARGS_NONE());   /* 15.2.20.5.6 */
+  mrb_define_method(mrb, io, "getc",       io_getc,       MRB_ARGS_NONE());   /* 15.2.20.5.8 */
   mrb_define_method(mrb, io, "read",       io_read,       MRB_ARGS_OPT(2));   /* 15.2.20.5.14 */
+  mrb_define_method(mrb, io, "readchar",   io_readchar,   MRB_ARGS_NONE());   /* 15.2.20.5.15 */
   mrb_define_method(mrb, io, "readline",   io_readline,   MRB_ARGS_OPT(2));   /* 15.2.20.5.16 */
   mrb_define_method(mrb, io, "sync",       io_sync,       MRB_ARGS_NONE());   /* 15.2.20.5.18 */
   mrb_define_method(mrb, io, "sync=",      io_set_sync,   MRB_ARGS_REQ(1));   /* 15.2.20.5.19 */
@@ -1889,7 +1892,6 @@ mrb_init_io(mrb_state *mrb)
   mrb_define_method(mrb, io, "write",      io_write,      MRB_ARGS_ANY());    /* 15.2.20.5.20 */
   mrb_define_method(mrb, io, "pread",      io_pread,      MRB_ARGS_ANY());    /* ruby 2.5 feature */
   mrb_define_method(mrb, io, "pwrite",     io_pwrite,     MRB_ARGS_ANY());    /* ruby 2.5 feature */
-  mrb_define_method(mrb, io, "readchar",   io_readchar,   MRB_ARGS_NONE());   /* 15.2.20.5.15 */
   mrb_define_method(mrb, io, "readbyte",   io_readbyte,   MRB_ARGS_NONE());
 
   mrb_define_const_id(mrb, io, MRB_SYM(SEEK_SET), mrb_fixnum_value(SEEK_SET));