2 files changed, 6 insertions, 2 deletions
diff --git a/tinyusb/class/cdc/cdc_device.c b/tinyusb/class/cdc/cdc_device.c
index 735a1ff72..9237e1945 100644
--- a/tinyusb/class/cdc/cdc_device.c
+++ b/tinyusb/class/cdc/cdc_device.c
@@ -314,11 +314,11 @@ tusb_error_t cdcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, tusb_event_t event, u
   return TUSB_ERROR_NONE;
 }
 
+#if CFG_TUD_CDC_FLUSH_ON_SOF
 void cdcd_sof(uint8_t rhport)
 {
-#if CFG_TUD_CDC_FLUSH_ON_SOF
   tud_n_cdc_flush(rhport);
-#endif
 }
+#endif
 
 #endif
diff --git a/tinyusb/class/cdc/cdc_device.h b/tinyusb/class/cdc/cdc_device.h
index 60b7a787b..c1a790fc8 100644
--- a/tinyusb/class/cdc/cdc_device.h
+++ b/tinyusb/class/cdc/cdc_device.h
@@ -102,7 +102,11 @@ tusb_error_t cdcd_control_request_st(uint8_t rhport, tusb_control_request_t cons
 tusb_error_t cdcd_xfer_cb(uint8_t rhport, uint8_t edpt_addr, tusb_event_t event, uint32_t xferred_bytes);
 void cdcd_close(uint8_t rhport);
 
+#if CFG_TUD_CDC_FLUSH_ON_SOF
 void cdcd_sof(uint8_t rhport);
+#else
+#define cdcd_sof    NULL
+#endif
 
 #endif