diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c
index 8fc66fa11c..2f4ed33173 100644
--- a/contrib/postgres_fdw/deparse.c
+++ b/contrib/postgres_fdw/deparse.c
@@ -3914,11 +3914,11 @@ appendOrderByClause(List *pathkeys, bool has_final_sort,
 	int			nestlevel;
 	const char *delim = " ";
 	StringInfo	buf = context->buf;
+	bool		gotone = false;
 
 	/* Make sure any constants in the exprs are printed portably */
 	nestlevel = set_transmission_modes();
 
-	appendStringInfoString(buf, " ORDER BY");
 	foreach(lcell, pathkeys)
 	{
 		PathKey    *pathkey = lfirst(lcell);
@@ -3949,6 +3949,21 @@ appendOrderByClause(List *pathkeys, bool has_final_sort,
 		if (em == NULL)
 			elog(ERROR, "could not find pathkey item to sort");
 
+		/*
+		 * If the member just has a Const expression then we needn't add it to
+		 * the ORDER BY clause.  This can happen in UNION ALL queries where the
+		 * union child targetlist has a Const.  Adding these would be wasteful,
+		 * but also, for INT columns, putting an integer literal will be seen
+		 * as an ordinal column position rather than a value to sort by, so we
+		 * must skip these.
+		 */
+		if (IsA(em->em_expr, Const))
+			continue;
+
+		if (!gotone)
+			appendStringInfoString(buf, " ORDER BY");
+		gotone = true;
+
 		em_expr = em->em_expr;
 
 		/*