diff --git a/src/backend/executor/functions.c b/src/backend/executor/functions.c
index e0bca7cb81c..37f616280c6 100644
--- a/src/backend/executor/functions.c
+++ b/src/backend/executor/functions.c
@@ -1728,8 +1728,9 @@ fmgr_sql(PG_FUNCTION_ARGS)
 				elog(ERROR, "failed to fetch lazy-eval tuple");
 			/* Extract the result as a datum, and copy out from the slot */
 			result = postquel_get_single_result(slot, fcinfo, fcache);
+			/* Clear the slot, in case it points into the tuplestore */
+			ExecClearTuple(slot);
 			/* Clear the tuplestore, but keep it for next time */
-			/* NB: this might delete the slot's content, but we don't care */
 			tuplestore_clear(fcache->tstore);
 
 			/*
@@ -1810,7 +1811,11 @@ fmgr_sql(PG_FUNCTION_ARGS)
 			/* Re-use the junkfilter's output slot to fetch back the tuple */
 			slot = fcache->junkFilter->jf_resultSlot;
 			if (tuplestore_gettupleslot(fcache->tstore, true, false, slot))
+			{
 				result = postquel_get_single_result(slot, fcinfo, fcache);
+				/* Clear the slot, in case it points into the tuplestore */
+				ExecClearTuple(slot);
+			}
 			else
 			{
 				fcinfo->isnull = true;