diff --git a/doc/src/sgml/queries.sgml b/doc/src/sgml/queries.sgml
index d8d4c3c53ef..b3cfbc93582 100644
--- a/doc/src/sgml/queries.sgml
+++ b/doc/src/sgml/queries.sgml
@@ -1162,7 +1162,7 @@ SELECT product_id, p.name, (sum(s.units) * p.price) AS sales
    <para>
     PostgreSQL also supports the syntax <literal>GROUP BY ALL</literal>,
     which is equivalent to explicitly writing all select-list entries that
-    do not contain either an aggregate function or a window function.
+    do not contain either an aggregate function referring to the same query level or a window function.
     This can greatly simplify ad-hoc exploration of data.
     As an example, these queries are equivalent:
 <screen>
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 09b6ce809bb..8d5a751af7e 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -862,7 +862,8 @@ GROUP BY { ALL | [ ALL | DISTINCT ] <replaceable class="parameter">grouping_elem
     <replaceable class="parameter">grouping_elements</replaceable>
     provided is equivalent to writing <literal>GROUP BY</literal> with the
     numbers of all <command>SELECT</command> output columns that do not
-    contain either an aggregate function or a window function.
+    contain either an aggregate function referring to the same query level or
+    a window function.
    </para>
 
    <para>
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 881fba2e7b5..2f7333e6786 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -2817,9 +2817,7 @@ transformGroupClause(ParseState *pstate, List *grouplist, bool groupByAll,
 
 			/*
 			 * Likewise, TLEs containing window functions are not okay to add
-			 * to GROUP BY.  At this writing, the SQL standard is silent on
-			 * what to do with them, but by analogy to aggregates we'll just
-			 * skip them.
+			 * to GROUP BY, and the SQL standard directs us to skip them.
 			 */
 			if (pstate->p_hasWindowFuncs &&
 				contain_windowfuncs((Node *) tle->expr))