diff --git a/cores/arduino/USB/CDC.cpp b/cores/arduino/USB/CDC.cpp
index 5a111dce9..67cc7f70e 100644
--- a/cores/arduino/USB/CDC.cpp
+++ b/cores/arduino/USB/CDC.cpp
@@ -163,8 +163,15 @@ void Serial_::end(void)
 
 void Serial_::accept(void)
 {
-	uint8_t buffer[CDC_SERIAL_BUFFER_SIZE];
-	uint32_t len = usb.recv(CDC_ENDPOINT_OUT, &buffer, CDC_SERIAL_BUFFER_SIZE);
+	uint32_t ringBufferSpace = availableForStore();
+	if (ringBufferSpace < EPX_SIZE) {
+		// usb.recv will always try to receive up to EPX_SIZE bytes on the endpoint
+		// make sure there is enough space, so that data is not lost
+		return;
+	}
+
+	uint8_t buffer[EPX_SIZE];
+	uint32_t len = usb.recv(CDC_ENDPOINT_OUT, &buffer, sizeof(buffer));
 
 	uint8_t enableInterrupts = ((__get_PRIMASK() & 0x1) == 0);
 	__disable_irq();
@@ -197,7 +204,8 @@ int Serial_::available(void)
 		return CDC_SERIAL_BUFFER_SIZE;
 	}
 	if (buffer->head == buffer->tail) {
-		USB->DEVICE.DeviceEndpoint[CDC_ENDPOINT_OUT].EPINTENSET.reg = USB_DEVICE_EPINTENCLR_TRCPT(1);
+		if (usb.available(CDC_ENDPOINT_OUT))
+			accept();
 	}
 	return (uint32_t)(CDC_SERIAL_BUFFER_SIZE + buffer->head - buffer->tail) % CDC_SERIAL_BUFFER_SIZE;
 }
@@ -236,8 +244,7 @@ int Serial_::read(void)
 		unsigned char c = buffer->buffer[buffer->tail];
 		buffer->tail = (uint32_t)(buffer->tail + 1) % CDC_SERIAL_BUFFER_SIZE;
 		buffer->full = false;
-// 		if (usb.available(CDC_ENDPOINT_OUT))
-// 			accept();
+
 		return c;
 	}
 }
@@ -345,6 +352,17 @@ bool Serial_::rts() {
 	return _usbLineInfo.lineState & 0x2;
 }
 
+int Serial_::availableForStore(void) {
+	ring_buffer *buffer = &cdc_rx_buffer;
+
+	if (buffer->full)
+		return 0;
+	else if (buffer->head >= buffer->tail)
+		return CDC_SERIAL_BUFFER_SIZE - 1 - buffer->head + buffer->tail;
+	else
+		return buffer->tail - buffer->head  - 1;
+}
+
 Serial_ SerialUSB(USBDevice);
 
 #endif
diff --git a/cores/arduino/USB/USBAPI.h b/cores/arduino/USB/USBAPI.h
index 1de826608..16adb6d09 100644
--- a/cores/arduino/USB/USBAPI.h
+++ b/cores/arduino/USB/USBAPI.h
@@ -167,6 +167,8 @@ class Serial_ : public Stream
 	};
 
 private:
+	int availableForStore(void);
+
 	USBDeviceClass &usb;
 	RingBuffer *_cdc_rx_buffer;
 };
diff --git a/cores/arduino/USB/USBCore.cpp b/cores/arduino/USB/USBCore.cpp
index cd356d578..bfd0a214c 100644
--- a/cores/arduino/USB/USBCore.cpp
+++ b/cores/arduino/USB/USBCore.cpp
@@ -245,12 +245,25 @@ void USBDeviceClass::handleEndpoint(uint8_t ep)
 #if defined(CDC_ENABLED)
 	if (ep == CDC_ENDPOINT_OUT)
 	{
-		// The RAM Buffer is empty: we can receive data
-		//usbd.epBank0ResetReady(CDC_ENDPOINT_OUT);
-
 		// Handle received bytes
 		if (available(CDC_ENDPOINT_OUT))
+		{
+			// always disable transfer complete,
+			// in case the CDC receive buffer is full
+			usbd.epBank0DisableTransferComplete(CDC_ENDPOINT_OUT);
+
 			SerialUSB.accept();
+		}
+		else
+		{
+			// ZLP received
+
+			// The RAM Buffer is empty: we can receive data
+			usbd.epBank0ResetReady(CDC_ENDPOINT_OUT);
+
+			// Clear Transfer complete 0 flag
+			usbd.epBank0AckTransferComplete(CDC_ENDPOINT_OUT);
+		}
 	}
 	if (ep == CDC_ENDPOINT_IN)
 	{
@@ -434,10 +447,6 @@ void USBDeviceClass::initEP(uint32_t ep, uint32_t config)
 	}
 	else if (config == USB_ENDPOINT_TYPE_CONTROL)
 	{
-		// XXX: Needed?
-// 		usbd.epBank0DisableAutoZLP(ep);
-// 		usbd.epBank1DisableAutoZLP(ep);
-
 		// Setup Control OUT
 		usbd.epBank0SetSize(ep, 64);
 		usbd.epBank0SetAddress(ep, &udd_ep_out_cache_buffer[ep]);
@@ -535,6 +544,9 @@ uint32_t USBDeviceClass::recv(uint32_t ep, void *_data, uint32_t len)
 
 		// Clear Transfer complete 0 flag
 		usbd.epBank0AckTransferComplete(ep);
+
+		// Enable Transfer complete 0 interrupt
+		usbd.epBank0EnableTransferComplete(ep);
 	}
 
 	return len;