diff --git a/src/class/cdc/cdc_device.c b/src/class/cdc/cdc_device.c
index 5a74b48766..c24edb7576 100644
--- a/src/class/cdc/cdc_device.c
+++ b/src/class/cdc/cdc_device.c
@@ -95,7 +95,8 @@ static void _prep_out_transaction (cdcd_interface_t* p_cdc)
   // fifo can be changed before endpoint is claimed
   available = tu_fifo_remaining(&p_cdc->rx_ff);
 
-  if ( available >= sizeof(p_cdc->epout_buf) )  {
+  if ( available >= sizeof(p_cdc->epout_buf) )
+  {
     usbd_edpt_xfer(rhport, p_cdc->ep_out, p_cdc->epout_buf, sizeof(p_cdc->epout_buf));
   }else
   {
@@ -432,25 +433,27 @@ bool cdcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint32_
   // Received new data
   if ( ep_addr == p_cdc->ep_out )
   {
-    // TODO search for wanted char first for better performance
-    for(uint32_t i=0; i<xferred_bytes; i++)
+    tu_fifo_write_n(&p_cdc->rx_ff, &p_cdc->epout_buf, xferred_bytes);
+    
+    // Check for wanted char and invoke callback if needed
+    if ( tud_cdc_rx_wanted_cb && (((signed char) p_cdc->wanted_char) != -1) )
     {
-      tu_fifo_write(&p_cdc->rx_ff, &p_cdc->epout_buf[i]);
-
-      // Check for wanted char and invoke callback if needed
-      if ( tud_cdc_rx_wanted_cb && ( ((signed char) p_cdc->wanted_char) != -1 ) && ( p_cdc->wanted_char == p_cdc->epout_buf[i] ) )
+      for ( uint32_t i = 0; i < xferred_bytes; i++ )
       {
-        tud_cdc_rx_wanted_cb(itf, p_cdc->wanted_char);
+        if ( (p_cdc->wanted_char == p_cdc->epout_buf[i]) && !tu_fifo_empty(&p_cdc->rx_ff) )
+        {
+          tud_cdc_rx_wanted_cb(itf, p_cdc->wanted_char);
+        }
       }
     }
-
+    
     // invoke receive callback (if there is still data)
-    if (tud_cdc_rx_cb && tu_fifo_count(&p_cdc->rx_ff) ) tud_cdc_rx_cb(itf);
-
+    if (tud_cdc_rx_cb && !tu_fifo_empty(&p_cdc->rx_ff) ) tud_cdc_rx_cb(itf);
+    
     // prepare for OUT transaction
     _prep_out_transaction(p_cdc);
   }
-
+  
   // Data sent to host, we continue to fetch from tx fifo to send.
   // Note: This will cause incorrect baudrate set in line coding.
   //       Though maybe the baudrate is not really important !!!