diff --git a/src/backend/executor/execGrouping.c b/src/backend/executor/execGrouping.c
index 4a8f72305ce..a69fa0f8cc3 100644
--- a/src/backend/executor/execGrouping.c
+++ b/src/backend/executor/execGrouping.c
@@ -236,9 +236,8 @@ BuildTupleHashTableExt(PlanState *parent,
 														hash_iv);
 
 	/* build comparator for all columns */
-	/* XXX: should we support non-minimal tuples for the inputslot? */
 	hashtable->tab_eq_func = ExecBuildGroupingEqual(inputDesc, inputDesc,
-													&TTSOpsMinimalTuple, &TTSOpsMinimalTuple,
+													NULL, &TTSOpsMinimalTuple,
 													numCols,
 													keyColIdx, eqfuncoids, collations,
 													allow_jit ? parent : NULL);
diff --git a/src/test/regress/expected/with.out b/src/test/regress/expected/with.out
index ff9754603bd..7a51e2eb757 100644
--- a/src/test/regress/expected/with.out
+++ b/src/test/regress/expected/with.out
@@ -656,6 +656,21 @@ SELECT t1.id, t2.path, t2 FROM t AS t1 JOIN t AS t2 ON
  16 | {3,7,11,16} | (16,"{3,7,11,16}")
 (16 rows)
 
+CREATE TEMP TABLE duplicates (a INT NOT NULL);
+INSERT INTO duplicates VALUES(1), (1);
+-- Try out a recursive UNION case where the non-recursive part's table slot
+-- uses TTSOpsBufferHeapTuple and contains duplicate rows.
+WITH RECURSIVE cte (a) as (
+	SELECT a FROM duplicates
+	UNION
+	SELECT a FROM cte
+)
+SELECT a FROM cte;
+ a 
+---
+ 1
+(1 row)
+
 -- test that column statistics from a materialized CTE are available
 -- to upper planner (otherwise, we'd get a stupider plan)
 explain (costs off)
diff --git a/src/test/regress/sql/with.sql b/src/test/regress/sql/with.sql
index aca7bae6ddd..dcdaab5eff0 100644
--- a/src/test/regress/sql/with.sql
+++ b/src/test/regress/sql/with.sql
@@ -361,6 +361,18 @@ UNION ALL
 SELECT t1.id, t2.path, t2 FROM t AS t1 JOIN t AS t2 ON
 (t1.id=t2.id);
 
+CREATE TEMP TABLE duplicates (a INT NOT NULL);
+INSERT INTO duplicates VALUES(1), (1);
+
+-- Try out a recursive UNION case where the non-recursive part's table slot
+-- uses TTSOpsBufferHeapTuple and contains duplicate rows.
+WITH RECURSIVE cte (a) as (
+	SELECT a FROM duplicates
+	UNION
+	SELECT a FROM cte
+)
+SELECT a FROM cte;
+
 -- test that column statistics from a materialized CTE are available
 -- to upper planner (otherwise, we'd get a stupider plan)
 explain (costs off)