diff --git a/src/backend/executor/functions.c b/src/backend/executor/functions.c
index e134a82ff7e..dc136251719 100644
--- a/src/backend/executor/functions.c
+++ b/src/backend/executor/functions.c
@@ -884,7 +884,7 @@ postquel_getnext(execution_state *es, SQLFunctionCachePtr fcache)
 	{
 		ProcessUtility(es->qd->plannedstmt,
 					   fcache->src,
-					   false,
+					   true,	/* protect function cache's parsetree */
 					   PROCESS_UTILITY_QUERY,
 					   es->qd->params,
 					   es->qd->queryEnv,