diff --git i/src/backend/tcop/postgres.c w/src/backend/tcop/postgres.c
index 49a3969..d5bd73f 100644
--- i/src/backend/tcop/postgres.c
+++ w/src/backend/tcop/postgres.c
@@ -3375,7 +3375,7 @@ process_postgres_switches(int argc, char *argv[], GucContext ctx)
 		if (IsUnderPostmaster)
 			ereport(FATAL,
 					(errcode(ERRCODE_SYNTAX_ERROR),
-				 errmsg("invalid command-line arguments for server process"),
+				 errmsg("invalid command-line arguments for server process: %s", argv[optind]),
 			  errhint("Try \"%s --help\" for more information.", progname)));
 		else
 			ereport(FATAL,