diff --git a/ChangeLog b/ChangeLog
index 5a8218d9c3..a9c1acbc0f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sun Apr 26 18:35:32 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* io.c (io_reopen): keeps pathv for prep_stdio.  [ruby-dev:38131]
+
 Sun Apr 26 15:13:09 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/optparse.rb (OptionParser#parse_in_order): do not make an
diff --git a/io.c b/io.c
index a043573a69..1d7b6eea81 100644
--- a/io.c
+++ b/io.c
@@ -5236,8 +5236,8 @@ io_reopen(VALUE io, VALUE nfile)
     fptr->mode = orig->mode | (fptr->mode & FMODE_PREP);
     fptr->pid = orig->pid;
     fptr->lineno = orig->lineno;
-    if (orig->pathv) fptr->pathv = orig->pathv;
-    else fptr->pathv = Qnil;
+    if (RTEST(orig->pathv)) fptr->pathv = orig->pathv;
+    else if (!IS_PREP_STDIO(fptr)) fptr->pathv = Qnil;
     fptr->finalize = orig->finalize;
 #if defined (__CYGWIN__) || !defined(HAVE_FORK)
     if (fptr->finalize == pipe_finalize)