diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index acbcb8bb81..dea995af09 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1231,7 +1231,7 @@ static struct config_bool ConfigureNamesBool[] =
 		{"is_superuser", PGC_INTERNAL, UNGROUPED,
 			gettext_noop("Shows whether the current user is a superuser."),
 			NULL,
-			GUC_REPORT | GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
+			GUC_REPORT | GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE | GUC_ALLOW_IN_PARALLEL
 		},
 		&session_auth_is_superuser,
 		false,
@@ -7562,10 +7562,12 @@ parse_and_validate_value(struct config_generic *record,
  *
  * Return value:
  *	+1: the value is valid and was successfully applied.
- *	0:	the name or value is invalid (but see below).
- *	-1: the value was not applied because of context, priority, or changeVal.
+ *	0:	the name or value is invalid, or it's invalid to try to set
+ *		this GUC now; but elevel was less than ERROR (see below).
+ *	-1: no error detected, but the value was not applied, either
+ *		because changeVal is false or there is some overriding setting.
  *
- * If there is an error (non-existing option, invalid value) then an
+ * If there is an error (non-existing option, invalid value, etc) then an
  * ereport(ERROR) is thrown *unless* this is called for a source for which
  * we don't want an ERROR (currently, those are defaults, the config file,
  * and per-database or per-user settings, as well as callers who specify
@@ -7645,6 +7647,10 @@ set_config_option_ext(const char *name, const char *value,
 			elevel = ERROR;
 	}
 
+	record = find_option(name, true, false, elevel);
+	if (record == NULL)
+		return 0;
+
 	/*
 	 * GUC_ACTION_SAVE changes are acceptable during a parallel operation,
 	 * because the current worker will also pop the change.  We're probably
@@ -7652,19 +7658,19 @@ set_config_option_ext(const char *name, const char *value,
 	 * body should observe the change, and peer workers do not share in the
 	 * execution of a function call started by this worker.
 	 *
+	 * Also allow normal setting if the GUC is marked GUC_ALLOW_IN_PARALLEL.
+	 *
 	 * Other changes might need to affect other workers, so forbid them.
 	 */
-	if (IsInParallelMode() && changeVal && action != GUC_ACTION_SAVE)
+	if (IsInParallelMode() && changeVal && action != GUC_ACTION_SAVE &&
+		(record->flags & GUC_ALLOW_IN_PARALLEL) == 0)
 	{
 		ereport(elevel,
 				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
-				 errmsg("cannot set parameters during a parallel operation")));
-		return -1;
-	}
-
-	record = find_option(name, true, false, elevel);
-	if (record == NULL)
+				 errmsg("parameter \"%s\" cannot be set during a parallel operation",
+						name)));
 		return 0;
+	}
 
 	/*
 	 * Check if the option can be set at this time. See guc.h for the precise
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 65eafb463b..e32bb0ab45 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -238,6 +238,7 @@ typedef enum
  * available via 'postgres -C' if the server is not running.
  */
 #define GUC_RUNTIME_COMPUTED  0x200000
+#define GUC_ALLOW_IN_PARALLEL 0x400000	/* allow setting in parallel mode */
 
 #define GUC_UNIT				(GUC_UNIT_MEMORY | GUC_UNIT_TIME)
 
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 91f74fe47a..2b5f9bfd40 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -1219,3 +1219,36 @@ SELECT 1 FROM tenk1_vw_sec
 (9 rows)
 
 rollback;
+-- test that function option SET ROLE works in parallel workers.
+create role regress_parallel_worker;
+create function set_and_report_role() returns text as
+  $$ select current_setting('role') $$ language sql parallel safe
+  set role = regress_parallel_worker;
+create function set_role_and_error(int) returns int as
+  $$ select 1 / $1 $$ language sql parallel safe
+  set role = regress_parallel_worker;
+set force_parallel_mode = 0;
+select set_and_report_role();
+   set_and_report_role   
+-------------------------
+ regress_parallel_worker
+(1 row)
+
+select set_role_and_error(0);
+ERROR:  division by zero
+CONTEXT:  SQL function "set_role_and_error" statement 1
+set force_parallel_mode = 1;
+select set_and_report_role();
+   set_and_report_role   
+-------------------------
+ regress_parallel_worker
+(1 row)
+
+select set_role_and_error(0);
+ERROR:  division by zero
+CONTEXT:  SQL function "set_role_and_error" statement 1
+parallel worker
+reset force_parallel_mode;
+drop function set_and_report_role();
+drop function set_role_and_error(int);
+drop role regress_parallel_worker;
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 62fb68c7a0..fb7c8b393b 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -462,3 +462,26 @@ SELECT 1 FROM tenk1_vw_sec
   WHERE (SELECT sum(f1) FROM int4_tbl WHERE f1 < unique1) < 100;
 
 rollback;
+
+-- test that function option SET ROLE works in parallel workers.
+create role regress_parallel_worker;
+
+create function set_and_report_role() returns text as
+  $$ select current_setting('role') $$ language sql parallel safe
+  set role = regress_parallel_worker;
+
+create function set_role_and_error(int) returns int as
+  $$ select 1 / $1 $$ language sql parallel safe
+  set role = regress_parallel_worker;
+
+set force_parallel_mode = 0;
+select set_and_report_role();
+select set_role_and_error(0);
+set force_parallel_mode = 1;
+select set_and_report_role();
+select set_role_and_error(0);
+reset force_parallel_mode;
+
+drop function set_and_report_role();
+drop function set_role_and_error(int);
+drop role regress_parallel_worker;