diff --git a/contrib/pg_upgrade/server.c b/contrib/pg_upgrade/server.c
index c1d459dd8220e79def97d220a4e3814a1634ad04..7e972315f8ecc1357664a8ad5f511298472bdeb3 100644
--- a/contrib/pg_upgrade/server.c
+++ b/contrib/pg_upgrade/server.c
@@ -190,7 +190,7 @@ start_postmaster(ClusterInfo *cluster, bool throw_error)
 #ifdef HAVE_UNIX_SOCKETS
 	/* prevent TCP/IP connections, restrict socket access */
 	strcat(socket_string,
-		   " -c listen_addresses='' -c unix_socket_permissions=0700");
+		   " -c listen_addresses=\"\" -c unix_socket_permissions=0700");
 
 	/* Have a sockdir?	Tell the postmaster. */
 	if (cluster->sockdir)