diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 0c593b81b4e..13527fc258f 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -3324,10 +3324,12 @@ 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
@@ -3390,8 +3392,11 @@ set_config_option_ext(const char *name, const char *value,
 
 
 /*
- * set_config_with_handle: takes an optional 'handle' argument, which can be
- * obtained by the caller from get_config_handle().
+ * set_config_with_handle: sets option `name' to given value.
+ *
+ * This API adds the ability to pass a 'handle' argument, which can be
+ * obtained by the caller from get_config_handle().  NULL has no effect,
+ * but a non-null value avoids the need to search the GUC tables.
  *
  * This should be used by callers which repeatedly set the same config
  * option(s), and want to avoid the overhead of a hash lookup each time.
@@ -3428,23 +3433,6 @@ set_config_with_handle(const char *name, config_handle *handle,
 			elevel = ERROR;
 	}
 
-	/*
-	 * GUC_ACTION_SAVE changes are acceptable during a parallel operation,
-	 * because the current worker will also pop the change.  We're probably
-	 * dealing with a function having a proconfig entry.  Only the function's
-	 * body should observe the change, and peer workers do not share in the
-	 * execution of a function call started by this worker.
-	 *
-	 * Other changes might need to affect other workers, so forbid them.
-	 */
-	if (IsInParallelMode() && changeVal && action != GUC_ACTION_SAVE)
-	{
-		ereport(elevel,
-				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
-				 errmsg("cannot set parameters during a parallel operation")));
-		return -1;
-	}
-
 	/* if handle is specified, no need to look up option */
 	if (!handle)
 	{
@@ -3455,6 +3443,27 @@ set_config_with_handle(const char *name, config_handle *handle,
 	else
 		record = handle;
 
+	/*
+	 * GUC_ACTION_SAVE changes are acceptable during a parallel operation,
+	 * because the current worker will also pop the change.  We're probably
+	 * dealing with a function having a proconfig entry.  Only the function's
+	 * 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 &&
+		(record->flags & GUC_ALLOW_IN_PARALLEL) == 0)
+	{
+		ereport(elevel,
+				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
+				 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
 	 * rules.
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 289dea7878a..636780673b8 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -1015,7 +1015,7 @@ 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
 		},
 		&current_role_is_superuser,
 		false,
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 4129ea37eec..ba6883ae8fc 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -223,6 +223,7 @@ typedef enum
 #define GUC_DISALLOW_IN_AUTO_FILE \
 							   0x002000 /* can't set in PG_AUTOCONF_FILENAME */
 #define GUC_RUNTIME_COMPUTED   0x004000 /* delay processing in 'postgres -C' */
+#define GUC_ALLOW_IN_PARALLEL  0x008000 /* allow setting in parallel mode */
 
 #define GUC_UNIT_KB			 0x01000000 /* value is in kilobytes */
 #define GUC_UNIT_BLOCKS		 0x02000000 /* value is in blocks */
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 68a629619a6..a61c138bd0a 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -1347,3 +1347,36 @@ select current_setting('session_authorization');
 (1 row)
 
 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 debug_parallel_query = 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 debug_parallel_query = 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 debug_parallel_query;
+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 1a0e7f144d0..22384b5ad85 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -520,3 +520,26 @@ select current_setting('session_authorization');
 set debug_parallel_query = 1;
 select current_setting('session_authorization');
 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 debug_parallel_query = 0;
+select set_and_report_role();
+select set_role_and_error(0);
+set debug_parallel_query = 1;
+select set_and_report_role();
+select set_role_and_error(0);
+reset debug_parallel_query;
+
+drop function set_and_report_role();
+drop function set_role_and_error(int);
+drop role regress_parallel_worker;