diff --git a/src/backend/access/transam/parallel.c b/src/backend/access/transam/parallel.c
index 194a1207be..7c39903249 100644
--- a/src/backend/access/transam/parallel.c
+++ b/src/backend/access/transam/parallel.c
@@ -1430,13 +1430,18 @@ ParallelWorkerMain(Datum main_arg)
 	 * variables.
 	 */
 	libraryspace = shm_toc_lookup(toc, PARALLEL_KEY_LIBRARY, false);
-	StartTransactionCommand();
 	RestoreLibraryState(libraryspace);
 
-	/* Restore GUC values from launching backend. */
+	/*
+	 * Restore GUC values from launching backend.  We want to do this without
+	 * starting a transaction as some GUC check hook functions require catalog
+	 * access.  It may be unsafe to access the catalogs as, for example,
+	 * reading buffer to load a catalog page may require writing dirty buffers
+	 * and we don't want to do that until I/O related GUCs such as fsync are
+	 * correctly set.
+	 */
 	gucspace = shm_toc_lookup(toc, PARALLEL_KEY_GUC, false);
 	RestoreGUCState(gucspace);
-	CommitTransactionCommand();
 
 	/* Crank up a transaction state appropriate to a parallel worker. */
 	tstatespace = shm_toc_lookup(toc, PARALLEL_KEY_TRANSACTION_STATE, false);
diff --git a/src/backend/commands/variable.c b/src/backend/commands/variable.c
index c361bb2079..a52ed5fa75 100644
--- a/src/backend/commands/variable.c
+++ b/src/backend/commands/variable.c
@@ -813,6 +813,14 @@ check_session_authorization(char **newval, void **extra, GucSource source)
 
 	if (!IsTransactionState())
 	{
+		/*
+		 * If we're a parallel worker being started up, there's no need to
+		 * verify the role exists.  We'll end up running the same snapshot as
+		 * the leader process anyway so the role must exist.
+		 */
+		if (InitializingParallelWorker)
+			return true;
+
 		/*
 		 * Can't do catalog lookups, so fail.  The result of this is that
 		 * session_authorization cannot be set in postgresql.conf, which seems