diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index 7be347c3d7..db1d7d3366 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -525,6 +525,9 @@ rewriteRuleAction(Query *parsetree,
 		 *
 		 * This could possibly be fixed by using some sort of internally
 		 * generated ID, instead of names, to link CTE RTEs to their CTEs.
+		 * However, decompiling the results would be quite confusing; note the
+		 * merge of hasRecursive flags below, which could change the apparent
+		 * semantics of such redundantly-named CTEs.
 		 */
 		foreach(lc, parsetree->cteList)
 		{
@@ -546,6 +549,26 @@ rewriteRuleAction(Query *parsetree,
 		/* OK, it's safe to combine the CTE lists */
 		sub_action->cteList = list_concat(sub_action->cteList,
 										  copyObject(parsetree->cteList));
+		/* ... and don't forget about the associated flags */
+		sub_action->hasRecursive |= parsetree->hasRecursive;
+		sub_action->hasModifyingCTE |= parsetree->hasModifyingCTE;
+
+		/*
+		 * If rule_action is different from sub_action (i.e., the rule action
+		 * is an INSERT...SELECT), then we might have just added some
+		 * data-modifying CTEs that are not at the top query level.  This is
+		 * disallowed by the parser and we mustn't generate such trees here
+		 * either, so throw an error.
+		 *
+		 * Conceivably such cases could be supported by attaching the original
+		 * query's CTEs to rule_action not sub_action.  But to do that, we'd
+		 * have to increment ctelevelsup in RTEs and SubLinks copied from the
+		 * original query.  For now, it doesn't seem worth the trouble.
+		 */
+		if (sub_action->hasModifyingCTE && rule_action != sub_action)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("INSERT...SELECT rule actions are not supported for queries having data-modifying statements in WITH")));
 	}
 
 	/*
diff --git a/src/test/regress/expected/with.out b/src/test/regress/expected/with.out
index 9b8c040dbe..b81620136a 100644
--- a/src/test/regress/expected/with.out
+++ b/src/test/regress/expected/with.out
@@ -1656,7 +1656,7 @@ SELECT * FROM bug6051;
 CREATE TEMP TABLE bug6051_2 (i int);
 CREATE RULE bug6051_ins AS ON INSERT TO bug6051 DO INSTEAD
  INSERT INTO bug6051_2
- SELECT NEW.i;
+ VALUES(NEW.i);
 WITH t1 AS ( DELETE FROM bug6051 RETURNING * )
 INSERT INTO bug6051 SELECT * FROM t1;
 SELECT * FROM bug6051;
@@ -1672,6 +1672,41 @@ SELECT * FROM bug6051_2;
  3
 (3 rows)
 
+-- check INSERT...SELECT rule actions are disallowed on commands
+-- that have modifyingCTEs
+CREATE OR REPLACE RULE bug6051_ins AS ON INSERT TO bug6051 DO INSTEAD
+ INSERT INTO bug6051_2
+ SELECT NEW.i;
+WITH t1 AS ( DELETE FROM bug6051 RETURNING * )
+INSERT INTO bug6051 SELECT * FROM t1;
+ERROR:  INSERT...SELECT rule actions are not supported for queries having data-modifying statements in WITH
+-- silly example to verify that hasModifyingCTE flag is propagated
+CREATE TEMP TABLE bug6051_3 AS
+  SELECT a FROM generate_series(11,13) AS a;
+CREATE RULE bug6051_3_ins AS ON INSERT TO bug6051_3 DO INSTEAD
+  SELECT i FROM bug6051_2;
+BEGIN; SET LOCAL force_parallel_mode = on;
+WITH t1 AS ( DELETE FROM bug6051_3 RETURNING * )
+  INSERT INTO bug6051_3 SELECT * FROM t1;
+ i 
+---
+ 1
+ 2
+ 3
+ 1
+ 2
+ 3
+ 1
+ 2
+ 3
+(9 rows)
+
+COMMIT;
+SELECT * FROM bug6051_3;
+ a 
+---
+(0 rows)
+
 -- a truly recursive CTE in the same list
 WITH RECURSIVE t(a) AS (
 	SELECT 0
diff --git a/src/test/regress/sql/with.sql b/src/test/regress/sql/with.sql
index b47880fa7b..bc6360eb9b 100644
--- a/src/test/regress/sql/with.sql
+++ b/src/test/regress/sql/with.sql
@@ -765,7 +765,7 @@ CREATE TEMP TABLE bug6051_2 (i int);
 
 CREATE RULE bug6051_ins AS ON INSERT TO bug6051 DO INSTEAD
  INSERT INTO bug6051_2
- SELECT NEW.i;
+ VALUES(NEW.i);
 
 WITH t1 AS ( DELETE FROM bug6051 RETURNING * )
 INSERT INTO bug6051 SELECT * FROM t1;
@@ -773,6 +773,31 @@ INSERT INTO bug6051 SELECT * FROM t1;
 SELECT * FROM bug6051;
 SELECT * FROM bug6051_2;
 
+-- check INSERT...SELECT rule actions are disallowed on commands
+-- that have modifyingCTEs
+CREATE OR REPLACE RULE bug6051_ins AS ON INSERT TO bug6051 DO INSTEAD
+ INSERT INTO bug6051_2
+ SELECT NEW.i;
+
+WITH t1 AS ( DELETE FROM bug6051 RETURNING * )
+INSERT INTO bug6051 SELECT * FROM t1;
+
+-- silly example to verify that hasModifyingCTE flag is propagated
+CREATE TEMP TABLE bug6051_3 AS
+  SELECT a FROM generate_series(11,13) AS a;
+
+CREATE RULE bug6051_3_ins AS ON INSERT TO bug6051_3 DO INSTEAD
+  SELECT i FROM bug6051_2;
+
+BEGIN; SET LOCAL force_parallel_mode = on;
+
+WITH t1 AS ( DELETE FROM bug6051_3 RETURNING * )
+  INSERT INTO bug6051_3 SELECT * FROM t1;
+
+COMMIT;
+
+SELECT * FROM bug6051_3;
+
 -- a truly recursive CTE in the same list
 WITH RECURSIVE t(a) AS (
 	SELECT 0