diff --git a/ChangeLog b/ChangeLog
index b1afd63407..cb944c7bf9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,8 @@ Sun Dec 27 20:54:22 2015  NAKAMURA Usaku  <usa@ruby-lang.org>
 	* process.c: use rb_w32_uchdir() instead of plain chdir() on Windows.
 	  reported by naruse via twitter.
 
+	* process.c (rb_execarg_addopt): need to convert to ospath.
+
 Sun Dec 27 20:00:31 2015  SHIBATA Hiroshi  <hsbt@ruby-lang.org>
 
 	* enc/x_emoji.h: fix dead-link.
diff --git a/process.c b/process.c
index e2ecceb438..fdf75ee019 100644
--- a/process.c
+++ b/process.c
@@ -1713,6 +1713,7 @@ rb_execarg_addopt(VALUE execarg_obj, VALUE key, VALUE val)
                 rb_raise(rb_eArgError, "chdir option specified twice");
             }
             FilePathValue(val);
+	    val = rb_str_encode_ospath(val);
             eargp->chdir_given = 1;
             eargp->chdir_dir = hide_obj(EXPORT_DUP(val));
         }