diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index eda9c1e42c..b2003f5672 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -4839,7 +4839,8 @@ text_to_table(PG_FUNCTION_ARGS)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("set-valued function called in context that cannot accept a set")));
-	if (!(rsi->allowedModes & SFRM_Materialize))
+	if (!(rsi->allowedModes & SFRM_Materialize) ||
+		rsi->expectedDesc == NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("materialize mode required, but it is not allowed in this context")));
diff --git a/src/backend/utils/misc/pg_config.c b/src/backend/utils/misc/pg_config.c
index d916d7b2c4..2dc875ebfb 100644
--- a/src/backend/utils/misc/pg_config.c
+++ b/src/backend/utils/misc/pg_config.c
@@ -37,11 +37,15 @@ pg_config(PG_FUNCTION_ARGS)
 	int			i = 0;
 
 	/* check to see if caller supports us returning a tuplestore */
-	if (!rsinfo || !(rsinfo->allowedModes & SFRM_Materialize))
+	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
 		ereport(ERROR,
-				(errcode(ERRCODE_SYNTAX_ERROR),
-				 errmsg("materialize mode required, but it is not "
-						"allowed in this context")));
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsinfo->allowedModes & SFRM_Materialize) ||
+		rsinfo->expectedDesc == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
 
 	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
 	oldcontext = MemoryContextSwitchTo(per_query_ctx);