diff --git a/src/backend/replication/syncrep.c b/src/backend/replication/syncrep.c
index cb6b5e5..93dd836 100644
--- a/src/backend/replication/syncrep.c
+++ b/src/backend/replication/syncrep.c
@@ -68,6 +68,7 @@
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
 #include "utils/builtins.h"
+#include "utils/memutils.h"
 #include "utils/ps_status.h"

 /* User-settable parameters for sync rep */
@@ -361,11 +362,6 @@ SyncRepInitConfig(void)
 {
 	int			priority;

-	/* Update the config data of synchronous replication */
-	SyncRepFreeConfig(SyncRepConfig);
-	SyncRepConfig = NULL;
-	SyncRepUpdateConfig();
-
 	/*
 	 * Determine if we are a potential sync standby and remember the result
 	 * for handling replies from standby.
@@ -868,42 +864,19 @@ SyncRepUpdateSyncStandbysDefined(void)
 }

 /*
- * Parse synchronous_standby_names and update the config data
- * of synchronous standbys.
- */
-void
-SyncRepUpdateConfig(void)
-{
-	int	parse_rc;
-
-	if (!SyncStandbysDefined())
-		return;
-
-	/*
-	 * check_synchronous_standby_names() verifies the setting value of
-	 * synchronous_standby_names before this function is called. So
-	 * syncrep_yyparse() must not cause an error here.
-	 */
-	syncrep_scanner_init(SyncRepStandbyNames);
-	parse_rc = syncrep_yyparse();
-	Assert(parse_rc == 0);
-	syncrep_scanner_finish();
-
-	SyncRepConfig = syncrep_parse_result;
-	syncrep_parse_result = NULL;
-}
-
-/*
  * Free a previously-allocated config data of synchronous replication.
  */
 void
-SyncRepFreeConfig(SyncRepConfigData *config)
+SyncRepFreeConfig(SyncRepConfigData *config, bool itself)
 {
 	if (!config)
 		return;

 	list_free_deep(config->members);
-	pfree(config);
+
+	if (itself)
+		free(config);
+
 }

 #ifdef USE_ASSERT_CHECKING
@@ -954,6 +927,10 @@ check_synchronous_standby_names(char **newval, void **extra, GucSource source)

 	if (*newval != NULL && (*newval)[0] != '\0')
 	{
+		MemoryContext oldcontext;
+
+		oldcontext = MemoryContextSwitchTo(TopMemoryContext);
+
 		syncrep_scanner_init(*newval);
 		parse_rc = syncrep_yyparse();
 		syncrep_scanner_finish();
@@ -1012,17 +989,36 @@ check_synchronous_standby_names(char **newval, void **extra, GucSource source)
 		}

 		/*
-		 * syncrep_yyparse sets the global syncrep_parse_result as side effect.
-		 * But this function is required to just check, so frees it
-		 * after parsing the parameter.
+		 * syncrep_yyparse sets the global syncrep_parse_result.
+		 * Save syncrep_parse_result to extra in order to use it in
+		 * assign_synchronous_standby_names hook as well.
 		 */
-		SyncRepFreeConfig(syncrep_parse_result);
+		*extra = (void *)syncrep_parse_result;
+
+		MemoryContextSwitchTo(oldcontext);
 	}

 	return true;
 }

 void
+assign_synchronous_standby_names(const char *newval, void *extra)
+{
+	SyncRepConfigData *myextra = extra;
+
+	/*
+	 * Free members of SyncRepConfig if it already refers somewhere,
+	 * but SyncRepConfig itself is freed by set_extra_field.
+	 */
+	if (SyncRepConfig)
+		SyncRepFreeConfig(SyncRepConfig, false);
+
+	SyncRepConfig = myextra;
+
+	return;
+}
+
+void
 assign_synchronous_commit(int newval, void *extra)
 {
 	switch (newval)
diff --git a/src/backend/replication/syncrep_gram.y b/src/backend/replication/syncrep_gram.y
index 380fedc..de25a40 100644
--- a/src/backend/replication/syncrep_gram.y
+++ b/src/backend/replication/syncrep_gram.y
@@ -76,7 +76,7 @@ static SyncRepConfigData *
 create_syncrep_config(char *num_sync, List *members)
 {
 	SyncRepConfigData *config =
-		(SyncRepConfigData *) palloc(sizeof(SyncRepConfigData));
+		(SyncRepConfigData *) malloc(sizeof(SyncRepConfigData));

 	config->num_sync = atoi(num_sync);
 	config->members = members;
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index e4a0119..a9c982b 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -2780,23 +2780,12 @@ pg_stat_get_wal_senders(PG_FUNCTION_ARGS)
 	MemoryContextSwitchTo(oldcontext);

 	/*
-	 * Allocate and update the config data of synchronous replication,
-	 * and then get the currently active synchronous standbys.
+	 * Get the currently active synchronous standbys.
 	 */
-	SyncRepUpdateConfig();
 	LWLockAcquire(SyncRepLock, LW_SHARED);
 	sync_standbys = SyncRepGetSyncStandbys(NULL);
 	LWLockRelease(SyncRepLock);

-	/*
-	 * Free the previously-allocated config data because a backend
-	 * no longer needs it. The next call of this function needs to
-	 * allocate and update the config data newly because the setting
-	 * of sync replication might be changed between the calls.
-	 */
-	SyncRepFreeConfig(SyncRepConfig);
-	SyncRepConfig = NULL;
-
 	for (i = 0; i < max_wal_senders; i++)
 	{
 		WalSnd *walsnd = &WalSndCtl->walsnds[i];
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index fb091bc..3ce83bf 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -3484,7 +3484,7 @@ static struct config_string ConfigureNamesString[] =
 		},
 		&SyncRepStandbyNames,
 		"",
-		check_synchronous_standby_names, NULL, NULL
+		check_synchronous_standby_names, assign_synchronous_standby_names, NULL
 	},

 	{
diff --git a/src/include/replication/syncrep.h b/src/include/replication/syncrep.h
index 14b5664..e1706f6 100644
--- a/src/include/replication/syncrep.h
+++ b/src/include/replication/syncrep.h
@@ -59,13 +59,13 @@ extern void SyncRepReleaseWaiters(void);

 /* called by wal sender and user backend */
 extern List *SyncRepGetSyncStandbys(bool *am_sync);
-extern void SyncRepUpdateConfig(void);
-extern void SyncRepFreeConfig(SyncRepConfigData *config);
+extern void SyncRepFreeConfig(SyncRepConfigData *config, bool itself);

 /* called by checkpointer */
 extern void SyncRepUpdateSyncStandbysDefined(void);

 extern bool check_synchronous_standby_names(char **newval, void **extra, GucSource source);
+extern void assign_synchronous_standby_names(const char *newval, void *extra);
 extern void assign_synchronous_commit(int newval, void *extra);

 /*