diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 1c5a2b43e9..cf554d389f 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1115,6 +1115,11 @@ connectOptions2(PGconn *conn)
 		{
 			if (ch->host)
 				free(ch->host);
+
+			/*
+			 * This bit selects the default host location.  If you change
+			 * this, see also pg_regress.
+			 */
 #ifdef HAVE_UNIX_SOCKETS
 			if (DEFAULT_PGSOCKET_DIR[0])
 			{
diff --git a/src/test/regress/pg_regress.c b/src/test/regress/pg_regress.c
index db8427dd9b..982801e029 100644
--- a/src/test/regress/pg_regress.c
+++ b/src/test/regress/pg_regress.c
@@ -746,10 +746,16 @@ initialize_environment(void)
 		 */
 		pghost = getenv("PGHOST");
 		pgport = getenv("PGPORT");
-#ifndef HAVE_UNIX_SOCKETS
 		if (!pghost)
-			pghost = "localhost";
+		{
+			/* Keep this bit in sync with libpq's default host location: */
+#ifdef HAVE_UNIX_SOCKETS
+			if (DEFAULT_PGSOCKET_DIR[0])
+				 /* do nothing, we'll print "Unix socket" below */ ;
+			else
 #endif
+				pghost = "localhost";	/* DefaultHost in fe-connect.c */
+		}
 
 		if (pghost && pgport)
 			printf(_("(using postmaster on %s, port %s)\n"), pghost, pgport);