diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 1e42d75465..bd01ec0526 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -1084,8 +1084,10 @@ preprocess_expression(PlannerInfo *root, Node *expr, int kind)
 
 	/*
 	 * Simplify constant expressions.  For function RTEs, this was already
-	 * done by preprocess_function_rtes ... but we have to do it again if the
-	 * RTE is LATERAL and might have contained join alias variables.
+	 * done by preprocess_function_rtes.  (But note we must do it again for
+	 * EXPRKIND_RTFUNC_LATERAL, because those might by now contain
+	 * un-simplified subexpressions inserted by flattening of subqueries or
+	 * join alias variables.)
 	 *
 	 * Note: an essential effect of this is to convert named-argument function
 	 * calls to positional notation and insert the current actual values of
@@ -1099,8 +1101,7 @@ preprocess_expression(PlannerInfo *root, Node *expr, int kind)
 	 * careful to maintain AND/OR flatness --- that is, do not generate a tree
 	 * with AND directly under AND, nor OR directly under OR.
 	 */
-	if (!(kind == EXPRKIND_RTFUNC ||
-		  (kind == EXPRKIND_RTFUNC_LATERAL && !root->hasJoinRTEs)))
+	if (kind != EXPRKIND_RTFUNC)
 		expr = eval_const_expressions(root, expr);
 
 	/*
diff --git a/src/test/regress/expected/rangefuncs.out b/src/test/regress/expected/rangefuncs.out
index cafca1f9ae..2334a1321e 100644
--- a/src/test/regress/expected/rangefuncs.out
+++ b/src/test/regress/expected/rangefuncs.out
@@ -2416,3 +2416,32 @@ select *, row_to_json(u) from unnest(array[]::rngfunc2[]) u;
 (0 rows)
 
 drop type rngfunc2;
+-- check handling of functions pulled up into function RTEs (bug #17227)
+explain (verbose, costs off)
+select * from
+  (select jsonb_path_query_array(module->'lectures', '$[*]') as lecture
+   from unnest(array['{"lectures": [{"id": "1"}]}'::jsonb])
+        as unnested_modules(module)) as ss,
+  jsonb_to_recordset(ss.lecture) as j (id text);
+                                                                       QUERY PLAN                                                                       
+--------------------------------------------------------------------------------------------------------------------------------------------------------
+ Nested Loop
+   Output: jsonb_path_query_array((unnested_modules.module -> 'lectures'::text), '$[*]'::jsonpath, '{}'::jsonb, false), j.id
+   ->  Function Scan on pg_catalog.unnest unnested_modules
+         Output: unnested_modules.module
+         Function Call: unnest('{"{\"lectures\": [{\"id\": \"1\"}]}"}'::jsonb[])
+   ->  Function Scan on pg_catalog.jsonb_to_recordset j
+         Output: j.id
+         Function Call: jsonb_to_recordset(jsonb_path_query_array((unnested_modules.module -> 'lectures'::text), '$[*]'::jsonpath, '{}'::jsonb, false))
+(8 rows)
+
+select * from
+  (select jsonb_path_query_array(module->'lectures', '$[*]') as lecture
+   from unnest(array['{"lectures": [{"id": "1"}]}'::jsonb])
+        as unnested_modules(module)) as ss,
+  jsonb_to_recordset(ss.lecture) as j (id text);
+    lecture    | id 
+---------------+----
+ [{"id": "1"}] | 1
+(1 row)
+
diff --git a/src/test/regress/sql/rangefuncs.sql b/src/test/regress/sql/rangefuncs.sql
index 3c436028da..7e5cde14c4 100644
--- a/src/test/regress/sql/rangefuncs.sql
+++ b/src/test/regress/sql/rangefuncs.sql
@@ -767,3 +767,18 @@ select *, row_to_json(u) from unnest(array[null::rngfunc2, (1,'foo')::rngfunc2,
 select *, row_to_json(u) from unnest(array[]::rngfunc2[]) u;
 
 drop type rngfunc2;
+
+-- check handling of functions pulled up into function RTEs (bug #17227)
+
+explain (verbose, costs off)
+select * from
+  (select jsonb_path_query_array(module->'lectures', '$[*]') as lecture
+   from unnest(array['{"lectures": [{"id": "1"}]}'::jsonb])
+        as unnested_modules(module)) as ss,
+  jsonb_to_recordset(ss.lecture) as j (id text);
+
+select * from
+  (select jsonb_path_query_array(module->'lectures', '$[*]') as lecture
+   from unnest(array['{"lectures": [{"id": "1"}]}'::jsonb])
+        as unnested_modules(module)) as ss,
+  jsonb_to_recordset(ss.lecture) as j (id text);