diff --git a/hash.c b/hash.c
index 5eba21654e..dda685012c 100644
--- a/hash.c
+++ b/hash.c
@@ -1715,7 +1715,7 @@ rb_hash_update_block_i(VALUE key, VALUE value, VALUE hash)
  *     hsh.update(other_hash){|key, oldval, newval| block}    => hsh
  *
  *  Adds the contents of <i>other_hash</i> to <i>hsh</i>.  If no
- *  block is specified entries with duplicate keys are overwritten
+ *  block is specified, entries with duplicate keys are overwritten
  *  with the values from <i>other_hash</i>, otherwise the value
  *  of each duplicate key is determined by calling the block with
  *  the key, its value in <i>hsh</i> and its value in <i>other_hash</i>.
@@ -1750,12 +1750,16 @@ rb_hash_update(VALUE hash1, VALUE hash2)
  *     hsh.merge(other_hash){|key, oldval, newval| block} -> a_hash
  *
  *  Returns a new hash containing the contents of <i>other_hash</i> and
- *  the contents of <i>hsh</i>, overwriting entries in <i>hsh</i> with
- *  duplicate keys with those from <i>other_hash</i>.
+ *  the contents of <i>hsh</i>. If no block is specified, the value for
+ *  entries with duplicate keys will be that of <i>other_hash</i>. Otherwise
+ *  the value for each duplicate key is determined by calling the block
+ *  with the key, its value in <i>hsh</i> and its value in <i>other_hash</i>.
  *
  *     h1 = { "a" => 100, "b" => 200 }
  *     h2 = { "b" => 254, "c" => 300 }
  *     h1.merge(h2)   #=> {"a"=>100, "b"=>254, "c"=>300}
+ *     h1.merge(h2){|key, oldval, newval| newval - oldval}
+ *                    #=> {"a"=>100, "b"=>54,  "c"=>300}
  *     h1             #=> {"a"=>100, "b"=>200}
  *
  */