diff --git a/ChangeLog b/ChangeLog
index 7171391e74..6f8d8df673 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Jul 30 23:14:44 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* io.c (rb_io_each_byte): rbuf can be refreshed during yield.
+	  [Bug #5119]
+
 Sat Jul 30 22:35:50 2011  Naohisa Goto  <ngotogenome@gmail.com>
 
 	* strftime.c (NEEDS): avoid SEGV due to integer overflow in
diff --git a/io.c b/io.c
index a1742637df..5fa8ba7aa8 100644
--- a/io.c
+++ b/io.c
@@ -2829,13 +2829,10 @@ rb_io_each_byte(VALUE io)
     GetOpenFile(io, fptr);
 
     for (;;) {
-	p = fptr->rbuf.ptr+fptr->rbuf.off;
-	e = p + fptr->rbuf.len;
-	while (p < e) {
-	    fptr->rbuf.off++;
-	    fptr->rbuf.len--;
+	while (fptr->rbuf.len > 0) {
+	    p = fptr->rbuf.ptr + fptr->rbuf.off++;
+	    e = p + fptr->rbuf.len--;
 	    rb_yield(INT2FIX(*p & 0xff));
-	    p++;
 	    errno = 0;
 	}
 	rb_io_check_byte_readable(fptr);
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index c62edbba00..d4787c75b4 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -235,6 +235,16 @@ class TestIO < Test::Unit::TestCase
     end)
   end
 
+  def test_each_byte_with_seek
+    t = make_tempfile
+    bug5119 = '[ruby-core:38609]'
+    i = 0
+    open(t.path) do |f|
+      f.each_byte {i = f.pos}
+    end
+    assert_equal(12, i, bug5119)
+  end
+
   def test_each_codepoint
     t = make_tempfile
     bug2959 = '[ruby-core:28650]'