diff --git a/ChangeLog b/ChangeLog
index bb6a5fbccd..2f1cf8ddfe 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Nov 16 06:39:31 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* pack.c (PACK_ITEM_ADJUST): return nil not result array and yield
+	  values if block is given.  [ruby-core:33193]
+
 Tue Nov 16 00:21:20 2010  Yusuke Endoh  <mame@tsg.ne.jp>
 
 	* regparse.c (and_cclass, or_cclass): fix memory leak.  Coverity Scan
diff --git a/pack.c b/pack.c
index 6befada66d..39a5922661 100644
--- a/pack.c
+++ b/pack.c
@@ -1221,7 +1221,7 @@ hex2num(char c)
 } while (0)
 
 #define PACK_ITEM_ADJUST() do { \
-    if (tmp_len > 0) \
+    if (tmp_len > 0 && !block_p) \
 	rb_ary_store(ary, RARRAY_LEN(ary)+tmp_len-1, Qnil); \
 } while (0)
 
diff --git a/test/ruby/test_pack.rb b/test/ruby/test_pack.rb
index 83b4582776..a668f7b218 100644
--- a/test/ruby/test_pack.rb
+++ b/test/ruby/test_pack.rb
@@ -630,4 +630,11 @@ class TestPack < Test::Unit::TestCase
       assert_equal([1,nil], str.unpack("#{fmt}2"))
     }
   end
+
+  def test_short_with_block
+    bug4059 = '[ruby-core:33193]'
+    result = :ok
+    assert_nil("".unpack("i") {|x| result = x}, bug4059)
+    assert_equal(:ok, result)
+  end
 end