*** a/src/backend/executor/execMain.c
--- b/src/backend/executor/execMain.c
***************
*** 1102,1112 **** CheckValidRowMarkRel(Relation rel, RowMarkType markType)
  							RelationGetRelationName(rel))));
  			break;
  		case RELKIND_MATVIEW:
! 			/* Should not get here */
! 			ereport(ERROR,
! 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
! 					 errmsg("cannot lock rows in materialized view \"%s\"",
! 							RelationGetRelationName(rel))));
  			break;
  		case RELKIND_FOREIGN_TABLE:
  			/* Should not get here */
--- 1102,1117 ----
  							RelationGetRelationName(rel))));
  			break;
  		case RELKIND_MATVIEW:
! 			/*
! 			 * Allow referencing rows from materialized views as long as no
! 			 * locking clause is involved.
! 			 */
! 			if (markType != ROW_MARK_REFERENCE &&
! 				markType != ROW_MARK_COPY)
! 				ereport(ERROR,
! 						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
! 						 errmsg("cannot lock rows in materialized view \"%s\"",
! 								RelationGetRelationName(rel))));
  			break;
  		case RELKIND_FOREIGN_TABLE:
  			/* Should not get here */
*** a/src/test/regress/expected/matview.out
--- b/src/test/regress/expected/matview.out
***************
*** 476,478 **** SELECT * FROM mv_v;
--- 476,489 ----
  
  DROP TABLE v CASCADE;
  NOTICE:  drop cascades to materialized view mv_v
+ -- make sure that matview rows can be referenced as source rows
+ CREATE TABLE base_table AS SELECT generate_series(1,10) AS a;
+ CREATE MATERIALIZED VIEW base_matview AS SELECT a FROM base_table;
+ DELETE FROM base_table USING base_matview WHERE base_matview.a = base_table.a;
+ SELECT * FROM base_table;
+  a 
+ ---
+ (0 rows)
+ 
+ DROP TABLE base_table CASCADE;
+ NOTICE:  drop cascades to materialized view base_matview
*** a/src/test/regress/sql/matview.sql
--- b/src/test/regress/sql/matview.sql
***************
*** 186,188 **** REFRESH MATERIALIZED VIEW CONCURRENTLY mv_v;
--- 186,195 ----
  SELECT * FROM v;
  SELECT * FROM mv_v;
  DROP TABLE v CASCADE;
+ 
+ -- make sure that matview rows can be referenced as source rows
+ CREATE TABLE base_table AS SELECT generate_series(1,10) AS a;
+ CREATE MATERIALIZED VIEW base_matview AS SELECT a FROM base_table;
+ DELETE FROM base_table USING base_matview WHERE base_matview.a = base_table.a;
+ SELECT * FROM base_table;
+ DROP TABLE base_table CASCADE;