diff -urpa postgresql-9.3.24.orig/contrib/pg_upgrade/option.c postgresql-9.3.24/contrib/pg_upgrade/option.c
--- postgresql-9.3.24.orig/contrib/pg_upgrade/option.c	2018-08-23 19:56:17.181401335 +0000
+++ postgresql-9.3.24/contrib/pg_upgrade/option.c	2018-08-23 19:59:38.729399066 +0000
@@ -411,6 +411,11 @@ get_sock_dir(ClusterInfo *cluster, bool
 			cluster->sockdir = pg_malloc(MAXPGPATH);
 			if (!getcwd(cluster->sockdir, MAXPGPATH))
 				pg_log(PG_FATAL, "cannot find current directory\n");
+#ifndef UNIX_PATH_MAX
+#define UNIX_PATH_MAX 108
+#endif
+			if (strlen(cluster->sockdir) > UNIX_PATH_MAX - sizeof(".s.PGSQL.50432"))
+				strcpy(cluster->sockdir, "/tmp"); /* fall back to tmp */
 		}
 		else
 		{
diff -urpa postgresql-9.3.24.orig/src/include/pg_config_manual.h postgresql-9.3.24/src/include/pg_config_manual.h
--- postgresql-9.3.24.orig/src/include/pg_config_manual.h	2018-08-23 19:56:17.195401335 +0000
+++ postgresql-9.3.24/src/include/pg_config_manual.h	2018-08-23 19:59:34.340399115 +0000
@@ -152,7 +152,7 @@
  * here's where to twiddle it.  You can also override this at runtime
  * with the postmaster's -k switch.
  */
-#define DEFAULT_PGSOCKET_DIR  "/tmp"
+#define DEFAULT_PGSOCKET_DIR  "/var/run/postgresql"
 
 /*
  * The random() function is expected to yield values between 0 and