diff --git a/configs/z80sim/src/z80_serial.c b/configs/z80sim/src/z80_serial.c
index 14de8e0e89..8fb59cadf6 100644
--- a/configs/z80sim/src/z80_serial.c
+++ b/configs/z80sim/src/z80_serial.c
@@ -129,7 +129,7 @@ static uart_dev_t g_uartport =
   },
   &g_uart_ops,              /* ops */
   NULL,                     /* priv */
-  NULL                      /* pollfds */
+  { NULL }                  /* pollfds */
 };
 
 /****************************************************************************