diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 8007e205ed..f20c31b9dc 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -3845,6 +3845,8 @@ create_grouping_paths(PlannerInfo *root,
 			|| grouping_is_sortable(parse->groupClause))
 			flags |= GROUPING_CAN_USE_SORT;
 
+		Assert(gd != NULL);
+
 		/*
 		 * Determine whether we should consider hash-based implementations of
 		 * grouping.