diff --git a/src/common/tusb_types.h b/src/common/tusb_types.h
index 5ab15aa3c..2b4ceb69c 100644
--- a/src/common/tusb_types.h
+++ b/src/common/tusb_types.h
@@ -48,7 +48,8 @@ typedef enum
 {
   TUSB_SPEED_FULL = 0,
   TUSB_SPEED_LOW     ,
-  TUSB_SPEED_HIGH
+  TUSB_SPEED_HIGH,
+  TUSB_SPEED_INVALID = 0xff,
 }tusb_speed_t;
 
 /// defined base on USB Specs Endpoint's bmAttributes
diff --git a/src/host/usbh.c b/src/host/usbh.c
index 10ae991f4..f278f4d94 100644
--- a/src/host/usbh.c
+++ b/src/host/usbh.c
@@ -153,7 +153,7 @@ tusb_device_state_t tuh_device_get_state (uint8_t const dev_addr)
 
 tusb_speed_t tuh_device_get_speed (uint8_t const dev_addr)
 {
-  TU_ASSERT( dev_addr <= CFG_TUSB_HOST_DEVICE_MAX, TUSB_DEVICE_STATE_UNPLUG);
+  TU_ASSERT( dev_addr <= CFG_TUSB_HOST_DEVICE_MAX, TUSB_SPEED_INVALID);
   return (tusb_speed_t) _usbh_devices[dev_addr].speed;
 }