diff --git a/ChangeLog b/ChangeLog
index 24788d0f2c..87e48a48e3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Thu Sep  4 23:42:42 2008  Tanaka Akira  <akr@fsij.org>
+
+	* include/ruby/intern.h (rb_file_open_str): declared.
+
+	* io.c (rb_file_open_str): defined.
+
+	* ext/zlib/zlib.c (gzfile_s_open): use rb_file_open_str instead of
+	  rb_file_open.
+
 Thu Sep  4 23:18:55 2008  Tanaka Akira  <akr@fsij.org>
 
 	* enc/trans/newline.trans: record newline types met in universal
diff --git a/ext/zlib/zlib.c b/ext/zlib/zlib.c
index 636ec325ce..9bb8f33344 100644
--- a/ext/zlib/zlib.c
+++ b/ext/zlib/zlib.c
@@ -2294,7 +2294,7 @@ gzfile_s_open(int argc, VALUE *argv, VALUE klass, const char *mode)
     }
     filename = argv[0];
     FilePathValue(filename);
-    io = rb_file_open(RSTRING_PTR(filename), mode);
+    io = rb_file_open_str(filename, mode);
 
     argv[0] = io;
     return rb_gzfile_s_wrap(argc, argv, klass);
diff --git a/include/ruby/intern.h b/include/ruby/intern.h
index 95e70c52be..a2010bb327 100644
--- a/include/ruby/intern.h
+++ b/include/ruby/intern.h
@@ -387,6 +387,7 @@ VALUE rb_io_print(int, VALUE*, VALUE);
 VALUE rb_io_puts(int, VALUE*, VALUE);
 VALUE rb_io_fdopen(int, int, const char*);
 VALUE rb_file_open(const char*, const char*);
+VALUE rb_file_open_str(VALUE, const char*);
 VALUE rb_gets(void);
 void rb_write_error(const char*);
 void rb_write_error2(const char*, long);
diff --git a/io.c b/io.c
index 4c8f41a924..ced821a6b5 100644
--- a/io.c
+++ b/io.c
@@ -4050,6 +4050,12 @@ rb_file_open_internal(VALUE io, VALUE filename, const char *mode)
             0666);
 }
 
+VALUE
+rb_file_open_str(VALUE fname, const char *mode)
+{
+    return rb_file_open_internal(io_alloc(rb_cFile), fname, mode);
+}
+
 VALUE
 rb_file_open(const char *fname, const char *mode)
 {