diff --git a/src/backend/optimizer/util/var.c b/src/backend/optimizer/util/var.c
index e57c3aa124..4e0b533e8f 100644
--- a/src/backend/optimizer/util/var.c
+++ b/src/backend/optimizer/util/var.c
@@ -579,7 +579,7 @@ locate_var_of_level_walker(Node *node,
  *	  Vars within a PHV's expression are included in the result only
  *	  when PVC_RECURSE_PLACEHOLDERS is specified.
  *
- *	  GroupingFuncs are treated mostly like Aggrefs, and so do not need
+ *	  GroupingFuncs are treated exactly like Aggrefs, and so do not need
  *	  their own flag bits.
  *
  *	  CurrentOfExpr nodes are ignored in all cases.
@@ -654,13 +654,7 @@ pull_var_clause_walker(Node *node, pull_var_clause_context *context)
 		}
 		else if (context->flags & PVC_RECURSE_AGGREGATES)
 		{
-			/*
-			 * We do NOT descend into the contained expression, even if the
-			 * caller asked for it, because we never actually evaluate it -
-			 * the result is driven entirely off the associated GROUP BY
-			 * clause, so we never need to extract the actual Vars here.
-			 */
-			return false;
+			/* fall through to recurse into the GroupingFunc's arguments */
 		}
 		else
 			elog(ERROR, "GROUPING found where not expected");
diff --git a/src/test/regress/expected/groupingsets.out b/src/test/regress/expected/groupingsets.out
index 29e6b52a45..2be94ed3c1 100644
--- a/src/test/regress/expected/groupingsets.out
+++ b/src/test/regress/expected/groupingsets.out
@@ -466,6 +466,70 @@ where x = 1 and q1 = 123;
 ---+----+-----
 (0 rows)
 
+-- check handling of pulled-up SubPlan in GROUPING() argument (bug #17479)
+explain (verbose, costs off)
+select grouping(ss.x)
+from int8_tbl i1
+cross join lateral (select (select i1.q1) as x) ss
+group by ss.x;
+                   QUERY PLAN                   
+------------------------------------------------
+ GroupAggregate
+   Output: GROUPING((SubPlan 1)), ((SubPlan 2))
+   Group Key: ((SubPlan 2))
+   ->  Sort
+         Output: ((SubPlan 2)), i1.q1
+         Sort Key: ((SubPlan 2))
+         ->  Seq Scan on public.int8_tbl i1
+               Output: (SubPlan 2), i1.q1
+               SubPlan 2
+                 ->  Result
+                       Output: i1.q1
+(11 rows)
+
+select grouping(ss.x)
+from int8_tbl i1
+cross join lateral (select (select i1.q1) as x) ss
+group by ss.x;
+ grouping 
+----------
+        0
+        0
+(2 rows)
+
+explain (verbose, costs off)
+select (select grouping(ss.x))
+from int8_tbl i1
+cross join lateral (select (select i1.q1) as x) ss
+group by ss.x;
+                 QUERY PLAN                 
+--------------------------------------------
+ GroupAggregate
+   Output: (SubPlan 2), ((SubPlan 3))
+   Group Key: ((SubPlan 3))
+   ->  Sort
+         Output: ((SubPlan 3)), i1.q1
+         Sort Key: ((SubPlan 3))
+         ->  Seq Scan on public.int8_tbl i1
+               Output: (SubPlan 3), i1.q1
+               SubPlan 3
+                 ->  Result
+                       Output: i1.q1
+   SubPlan 2
+     ->  Result
+           Output: GROUPING((SubPlan 1))
+(14 rows)
+
+select (select grouping(ss.x))
+from int8_tbl i1
+cross join lateral (select (select i1.q1) as x) ss
+group by ss.x;
+ grouping 
+----------
+        0
+        0
+(2 rows)
+
 -- simple rescan tests
 select a, b, sum(v.x)
   from (values (1),(2)) v(x), gstest_data(v.x)
diff --git a/src/test/regress/sql/groupingsets.sql b/src/test/regress/sql/groupingsets.sql
index c0786bbed8..71d2ae9a05 100644
--- a/src/test/regress/sql/groupingsets.sql
+++ b/src/test/regress/sql/groupingsets.sql
@@ -188,6 +188,29 @@ select * from (
 ) ss
 where x = 1 and q1 = 123;
 
+-- check handling of pulled-up SubPlan in GROUPING() argument (bug #17479)
+explain (verbose, costs off)
+select grouping(ss.x)
+from int8_tbl i1
+cross join lateral (select (select i1.q1) as x) ss
+group by ss.x;
+
+select grouping(ss.x)
+from int8_tbl i1
+cross join lateral (select (select i1.q1) as x) ss
+group by ss.x;
+
+explain (verbose, costs off)
+select (select grouping(ss.x))
+from int8_tbl i1
+cross join lateral (select (select i1.q1) as x) ss
+group by ss.x;
+
+select (select grouping(ss.x))
+from int8_tbl i1
+cross join lateral (select (select i1.q1) as x) ss
+group by ss.x;
+
 -- simple rescan tests
 
 select a, b, sum(v.x)