diff --git a/ChangeLog b/ChangeLog
index 3a3f858a34..ee043d61ca 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Feb 21 14:47:09 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* io.c (argf_set_encoding): uses current_file after check for next
+	  input.
+
 Thu Feb 21 11:10:49 2008  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* string.c: replace rb_enc_copy by rb_enc_cr_str_copy or
diff --git a/bootstraptest/test_io.rb b/bootstraptest/test_io.rb
index 4974a1eeb9..07211050a6 100644
--- a/bootstraptest/test_io.rb
+++ b/bootstraptest/test_io.rb
@@ -69,3 +69,7 @@ assert_equal 'ok', %q{
   File.unlink(tmpname)
   :ok
 }
+
+assert_normal_exit %q{
+  ARGF.set_encoding "foo"
+}
diff --git a/bootstraptest/test_knownbug.rb b/bootstraptest/test_knownbug.rb
index 7a697c76b8..c438231f2c 100644
--- a/bootstraptest/test_knownbug.rb
+++ b/bootstraptest/test_knownbug.rb
@@ -57,7 +57,3 @@ assert_normal_exit %q{
 assert_normal_exit %q{
   "".center(1, "\x80".force_encoding("utf-8"))
 }, '[ruby-dev:33807]'
-
-assert_normal_exit %q{
-  ARGF.set_encoding "foo"
-}
diff --git a/io.c b/io.c
index 1b98b6ae0d..c17fc9e93f 100644
--- a/io.c
+++ b/io.c
@@ -6103,8 +6103,11 @@ argf_set_encoding(int argc, VALUE *argv, VALUE io)
 {
     rb_io_t *fptr;
 
+    if (next_argv()) {
+	rb_raise(rb_eArgError, "no stream to set encoding");
+    }
     rb_io_set_encoding(argc, argv, current_file);
-    GetOpenFile(io, fptr);
+    GetOpenFile(current_file, fptr);
     argf_enc = fptr->enc;
     argf_enc2 = fptr->enc2;
     return io;