diff --git a/ChangeLog b/ChangeLog
index cd15e2d47a..c67fdc0cfc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+Tue Jul 30 17:16:15 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* sprintf.c (ruby__sfvextra): add QUOTE flag to escape unprintable
+	  characters.
+
+Tue Jul 30 17:09:51 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* sprintf.c (ruby__sfvextra): add QUOTE flag to escape unprintable
+	  characters.
+
 Tue Jul 30 11:00:52 2013  Zachary Scott  <e@zzak.io>
 
 	* ext/curses/extconf.rb: [DOC] nodoc to reduce Object pollution
diff --git a/ext/-test-/printf/printf.c b/ext/-test-/printf/printf.c
index 775eb33dc7..28a158beb4 100644
--- a/ext/-test-/printf/printf.c
+++ b/ext/-test-/printf/printf.c
@@ -21,6 +21,12 @@ printf_test_v(VALUE self, VALUE obj)
     return rb_enc_sprintf(rb_usascii_encoding(), "{%+"PRIsVALUE"}", obj);
 }
 
+static VALUE
+printf_test_q(VALUE self, VALUE obj)
+{
+    return rb_enc_sprintf(rb_usascii_encoding(), "[% "PRIsVALUE"]", obj);
+}
+
 void
 Init_printf(void)
 {
@@ -28,4 +34,5 @@ Init_printf(void)
     rb_define_singleton_method(m, "i", printf_test_i, 1);
     rb_define_singleton_method(m, "s", printf_test_s, 1);
     rb_define_singleton_method(m, "v", printf_test_v, 1);
+    rb_define_singleton_method(m, "q", printf_test_q, 1);
 }
diff --git a/sprintf.c b/sprintf.c
index 09876bf812..97b2126422 100644
--- a/sprintf.c
+++ b/sprintf.c
@@ -1171,6 +1171,7 @@ ruby__sfvextra(rb_printf_buffer *fp, size_t valsize, void *valp, long *sz, int s
     }
     else {
 	value = rb_obj_as_string(value);
+	if (sign == ' ') value = QUOTE(value);
     }
     enc = rb_enc_compatible(result, value);
     if (enc) {
diff --git a/test/-ext-/test_printf.rb b/test/-ext-/test_printf.rb
index 29f384b1d7..4532c371b4 100644
--- a/test/-ext-/test_printf.rb
+++ b/test/-ext-/test_printf.rb
@@ -22,6 +22,12 @@ class Test_SPrintf < Test::Unit::TestCase
     assert_equal("{<#{self.class}:#{object_id}>}", Bug::Printf.v(self))
   end
 
+  def test_quote
+    assert_equal('["\n"]', Bug::Printf.q("\n"))
+    assert_equal('[aaa]', Bug::Printf.q('aaa'))
+    assert_equal('[a a]', Bug::Printf.q('a a'))
+  end
+
   def test_encoding
     def self.to_s
       "\u{3042 3044 3046 3048 304a}"