diff --git a/doc/src/sgml/ref/comment.sgml b/doc/src/sgml/ref/comment.sgml
index ae4640b6235..115889ef58f 100644
--- a/doc/src/sgml/ref/comment.sgml
+++ b/doc/src/sgml/ref/comment.sgml
@@ -80,14 +80,16 @@ COMMENT ON
   <title>Description</title>
 
   <para>
-   <command>COMMENT</command> stores a comment about a database object.
+   <command>COMMENT</command> stores, replaces, or removes the comment on a
+   database object.
   </para>
 
   <para>
-   Only one comment string is stored for each object, so to modify a comment,
-   issue a new <command>COMMENT</command> command for the same object.  To remove a
-   comment, write <literal>NULL</literal> in place of the text string.
-   Comments are automatically dropped when their object is dropped.
+   Only one comment string is stored for each object.  Issuing a new
+   <command>COMMENT</command> command for the same object replaces the
+   existing comment.  Specifying <literal>NULL</literal> or an empty
+   string (<literal>''</literal>) removes the comment.  Comments are
+   automatically dropped when their object is dropped.
   </para>
 
   <para>
@@ -265,7 +267,8 @@ COMMENT ON
     <term><replaceable class="parameter">string_literal</replaceable></term>
     <listitem>
      <para>
-      The new comment contents, written as a string literal.
+      The new comment contents, written as a string literal.  An empty string
+      (<literal>''</literal>) removes the comment.
      </para>
     </listitem>
    </varlistentry>
@@ -274,7 +277,7 @@ COMMENT ON
     <term><literal>NULL</literal></term>
     <listitem>
      <para>
-      Write <literal>NULL</literal> to drop the comment.
+      Write <literal>NULL</literal> to remove the comment.
      </para>
     </listitem>
    </varlistentry>
@@ -361,6 +364,7 @@ COMMENT ON TRANSFORM FOR hstore LANGUAGE plpythonu IS 'Transform between hstore
 COMMENT ON TRIGGER my_trigger ON my_table IS 'Used for RI';
 COMMENT ON TYPE complex IS 'Complex number data type';
 COMMENT ON VIEW my_view IS 'View of departmental costs';
+COMMENT ON VIEW my_view IS NULL;
 </programlisting></para>
  </refsect1>
 
diff --git a/src/test/regress/expected/create_index.out b/src/test/regress/expected/create_index.out
index be80774dd4f..ad8de5b3a6f 100644
--- a/src/test/regress/expected/create_index.out
+++ b/src/test/regress/expected/create_index.out
@@ -30,6 +30,20 @@ COMMENT ON INDEX six_wrong IS 'bad index';
 ERROR:  relation "six_wrong" does not exist
 COMMENT ON INDEX six IS 'good index';
 COMMENT ON INDEX six IS NULL;
+SELECT obj_description('six'::regclass, 'pg_class') IS NULL AS six_comment_is_null;
+ six_comment_is_null 
+---------------------
+ t
+(1 row)
+
+COMMENT ON INDEX six IS 'add the comment back';
+COMMENT ON INDEX six IS ''; -- empty string removes the comment, same as NULL
+SELECT obj_description('six'::regclass, 'pg_class') IS NULL AS six_comment_is_null;
+ six_comment_is_null 
+---------------------
+ t
+(1 row)
+
 --
 -- BTREE ascending/descending cases
 --
diff --git a/src/test/regress/sql/create_index.sql b/src/test/regress/sql/create_index.sql
index b4c49405ae2..47d6124aebb 100644
--- a/src/test/regress/sql/create_index.sql
+++ b/src/test/regress/sql/create_index.sql
@@ -42,6 +42,10 @@ CREATE INDEX six ON shighway USING btree (name text_ops);
 COMMENT ON INDEX six_wrong IS 'bad index';
 COMMENT ON INDEX six IS 'good index';
 COMMENT ON INDEX six IS NULL;
+SELECT obj_description('six'::regclass, 'pg_class') IS NULL AS six_comment_is_null;
+COMMENT ON INDEX six IS 'add the comment back';
+COMMENT ON INDEX six IS ''; -- empty string removes the comment, same as NULL
+SELECT obj_description('six'::regclass, 'pg_class') IS NULL AS six_comment_is_null;
 
 --
 -- BTREE ascending/descending cases