diff --git a/src/backend/catalog/aclchk.c b/src/backend/catalog/aclchk.c
index 5f1726c095..d65bf47d77 100644
--- a/src/backend/catalog/aclchk.c
+++ b/src/backend/catalog/aclchk.c
@@ -5045,6 +5045,9 @@ pg_database_aclcheck(Oid db_oid, Oid roleid, AclMode mode)
 AclResult
 pg_parameter_aclcheck(const char *name, Oid roleid, AclMode mode)
 {
+	/* It's pointless to call this function, unless we're in a transaction. */
+	Assert(IsTransactionState());
+
 	if (pg_parameter_aclmask(name, roleid, mode, ACLMASK_ANY) != 0)
 		return ACLCHECK_OK;
 	else
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 8b6b5bbaaa..e63548777e 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -4163,12 +4163,6 @@ PostgresMain(const char *dbname, const char *username)
 	if (am_walsender)
 		InitWalSender();
 
-	/*
-	 * process any libraries that should be preloaded at backend start (this
-	 * likewise can't be done until GUC settings are complete)
-	 */
-	process_session_preload_libraries();
-
 	/*
 	 * Send this backend's cancellation info to the frontend.
 	 */
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 6b9082604f..29f7adb0a7 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -1108,6 +1108,13 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
 	/* Initialize this backend's session state. */
 	InitializeSession();
 
+	/*
+	 * process any libraries that should be preloaded at backend start (this
+	 * can't be done until GUC settings are complete). Note that these libraries
+	 * can declare new GUC variables.
+	 */
+	process_session_preload_libraries();
+
 	/* report this backend in the PgBackendStatus array */
 	if (!bootstrap)
 		pgstat_bestart();