diff --git a/src/backend/executor/nodeGatherMerge.c b/src/backend/executor/nodeGatherMerge.c
index 72f30ab..e19bace 100644
--- a/src/backend/executor/nodeGatherMerge.c
+++ b/src/backend/executor/nodeGatherMerge.c
@@ -431,9 +431,14 @@ gather_merge_clear_slots(GatherMergeState *gm_state)
 {
 	int			i;
 
-	for (i = 0; i < gm_state->nreaders; i++)
+	for (i = 0; i < gm_state->nreaders + 1; i++)
 	{
-		pfree(gm_state->gm_tuple_buffers[i].tuple);
+		/*
+		 * Gather merge always allow leader to participate and we don't
+		 * allocate the tuple, so no need to free the tuple for leader.
+		 */
+		if (i != gm_state->nreaders)
+			pfree(gm_state->gm_tuple_buffers[i].tuple);
 		gm_state->gm_slots[i] = ExecClearTuple(gm_state->gm_slots[i]);
 	}
 
@@ -474,6 +479,8 @@ gather_merge_getnext(GatherMergeState *gm_state)
 		 */
 		i = DatumGetInt32(binaryheap_first(gm_state->gm_heap));
 
+		Assert(i < gm_state->nreaders + 1);
+
 		if (gather_merge_readnext(gm_state, i, false))
 			binaryheap_replace_first(gm_state->gm_heap, Int32GetDatum(i));
 		else