diff --git a/README.md b/README.md
index 05f3521c..072dfc84 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 ![tinyUSB_240x100](https://user-images.githubusercontent.com/249515/62646655-f9393200-b978-11e9-9c53-484862f15503.png)
 
-[![Build Status](https://github.com/hathach/tinyusb/workflows/Build/badge.svg)](https://github.com/hathach/tinyusb/actions) [![License](https://img.shields.io/badge/license-MIT-brightgreen.svg)](https://opensource.org/licenses/MIT) [![Coverity](https://img.shields.io/coverity/scan/458.svg)](https://scan.coverity.com/projects/tinyusb)
+[![Build Status](https://github.com/hathach/tinyusb/workflows/Build/badge.svg)](https://github.com/hathach/tinyusb/actions) [![License](https://img.shields.io/badge/license-MIT-brightgreen.svg)](https://opensource.org/licenses/MIT)
 
 TinyUSB is an open-source cross-platform USB Host/Device stack for embedded system, designed to be memory-safe with no dynamic allocation and thread-safe with all interrupt events are deferred then handled in the non-ISR task function.
 
diff --git a/src/class/cdc/cdc_device.c b/src/class/cdc/cdc_device.c
index e39adc5f..e54b7d26 100644
--- a/src/class/cdc/cdc_device.c
+++ b/src/class/cdc/cdc_device.c
@@ -34,6 +34,11 @@
 //--------------------------------------------------------------------+
 // MACRO CONSTANT TYPEDEF
 //--------------------------------------------------------------------+
+enum
+{
+  BULK_PACKET_SIZE = (TUD_OPT_HIGH_SPEED ? 512 : 64)
+};
+
 typedef struct
 {
   uint8_t itf_num;
@@ -160,13 +165,11 @@ uint32_t tud_cdc_n_write(uint8_t itf, void const* buffer, uint32_t bufsize)
   cdcd_interface_t* p_cdc = &_cdcd_itf[itf];
   uint16_t ret = tu_fifo_write_n(&p_cdc->tx_ff, buffer, bufsize);
 
-#if 0 // TODO issue with circuitpython's REPL
-  // flush if queue more than endpoint size
-  if ( tu_fifo_count(&p_cdc->tx_ff) >= CFG_TUD_CDC_EP_BUFSIZE )
+  // flush if queue more than packet size
+  if ( tu_fifo_count(&p_cdc->tx_ff) >= BULK_PACKET_SIZE )
   {
     tud_cdc_n_write_flush(itf);
   }
-#endif
 
   return ret;
 }
@@ -250,8 +253,8 @@ void cdcd_reset(uint8_t rhport)
 uint16_t cdcd_open(uint8_t rhport, tusb_desc_interface_t const * itf_desc, uint16_t max_len)
 {
   // Only support ACM subclass
-  TU_VERIFY ( TUSB_CLASS_CDC                           == itf_desc->bInterfaceClass &&
-              CDC_COMM_SUBCLASS_ABSTRACT_CONTROL_MODEL == itf_desc->bInterfaceSubClass, 0);
+  TU_VERIFY( TUSB_CLASS_CDC                           == itf_desc->bInterfaceClass &&
+             CDC_COMM_SUBCLASS_ABSTRACT_CONTROL_MODEL == itf_desc->bInterfaceSubClass, 0);
 
   // Note: 0xFF can be used with RNDIS
   TU_VERIFY(tu_within(CDC_COMM_PROTOCOL_NONE, itf_desc->bInterfaceProtocol, CDC_COMM_PROTOCOL_ATCOMMAND_CDMA), 0);
@@ -446,9 +449,8 @@ bool cdcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint32_
     if ( 0 == tud_cdc_n_write_flush(itf) )
     {
       // If there is no data left, a ZLP should be sent if
-      // xferred_bytes is multiple of EP size and not zero
-      // FIXME CFG_TUD_CDC_EP_BUFSIZE is not Endpoint packet size
-      if ( !tu_fifo_count(&p_cdc->tx_ff) && xferred_bytes && (0 == (xferred_bytes % CFG_TUD_CDC_EP_BUFSIZE)) )
+      // xferred_bytes is multiple of EP Packet size and not zero
+      if ( !tu_fifo_count(&p_cdc->tx_ff) && xferred_bytes && (0 == (xferred_bytes & (BULK_PACKET_SIZE-1))) )
       {
         if ( usbd_edpt_claim(rhport, p_cdc->ep_in) )
         {