diff --git a/demos/STM32/RT-AT32F435-ARTERY144/cfg/halconf.h b/demos/STM32/RT-AT32F435-ARTERY144/cfg/halconf.h
index 6dba79884..a310f42fb 100644
--- a/demos/STM32/RT-AT32F435-ARTERY144/cfg/halconf.h
+++ b/demos/STM32/RT-AT32F435-ARTERY144/cfg/halconf.h
@@ -450,7 +450,7 @@
  *          buffers.
  */
 #if !defined(SERIAL_USB_BUFFERS_SIZE) || defined(__DOXYGEN__)
-#define SERIAL_USB_BUFFERS_SIZE             256
+#define SERIAL_USB_BUFFERS_SIZE             64
 #endif
 
 /**
@@ -458,7 +458,7 @@
  * @note    The default is 2 buffers.
  */
 #if !defined(SERIAL_USB_BUFFERS_NUMBER) || defined(__DOXYGEN__)
-#define SERIAL_USB_BUFFERS_NUMBER           2
+#define SERIAL_USB_BUFFERS_NUMBER           8
 #endif
 
 /*===========================================================================*/
diff --git a/os/hal/include/hal_serial_usb.h b/os/hal/include/hal_serial_usb.h
index 0e32429d3..076032768 100644
--- a/os/hal/include/hal_serial_usb.h
+++ b/os/hal/include/hal_serial_usb.h
@@ -59,6 +59,22 @@
 #if !defined(SERIAL_USB_BUFFERS_NUMBER) || defined(__DOXYGEN__)
 #define SERIAL_USB_BUFFERS_NUMBER   2
 #endif
+
+#if !defined(SERIAL_USB_BUFFERS_RX_SIZE) ||  defined(__DOXYGEN__)
+#define SERIAL_USB_BUFFERS_RX_SIZE  SERIAL_USB_BUFFERS_SIZE
+#endif
+
+#if !defined(SERIAL_USB_BUFFERS_RX_NUMBER) ||  defined(__DOXYGEN__)
+#define SERIAL_USB_BUFFERS_RX_NUMBER  SERIAL_USB_BUFFERS_NUMBER
+#endif
+
+#if !defined(SERIAL_USB_BUFFERS_TX_SIZE) ||  defined(__DOXYGEN__)
+#define SERIAL_USB_BUFFERS_TX_SIZE  SERIAL_USB_BUFFERS_SIZE
+#endif
+
+#if !defined(SERIAL_USB_BUFFERS_TX_NUMBER) ||  defined(__DOXYGEN__)
+#define SERIAL_USB_BUFFERS_TX_NUMBER  SERIAL_USB_BUFFERS_NUMBER
+#endif
 /** @} */
 
 /*===========================================================================*/
@@ -69,6 +85,10 @@
 #error "Serial over USB Driver requires HAL_USE_USB"
 #endif
 
+#if (SERIAL_USB_BUFFERS_RX_SIZE != 64)
+#error "Please keep SERIAL_USB_BUFFERS_SIZE until https://forum.chibios.org/viewtopic.php?f=35&t=6395 is properly fixed!"
+#endif
+
 /*===========================================================================*/
 /* Driver data structures and types.                                         */
 /*===========================================================================*/
@@ -125,11 +145,11 @@ typedef struct {
   /* Output queue.*/                                                        \
   output_buffers_queue_t    obqueue;                                        \
   /* Input buffer.*/                                                        \
-  uint8_t                   ib[BQ_BUFFER_SIZE(SERIAL_USB_BUFFERS_NUMBER,    \
-                                              SERIAL_USB_BUFFERS_SIZE)];    \
+  uint8_t                   ib[BQ_BUFFER_SIZE(SERIAL_USB_BUFFERS_RX_NUMBER, \
+                                              SERIAL_USB_BUFFERS_RX_SIZE)]; \
   /* Output buffer.*/                                                       \
-  uint8_t                   ob[BQ_BUFFER_SIZE(SERIAL_USB_BUFFERS_NUMBER,    \
-                                              SERIAL_USB_BUFFERS_SIZE)];    \
+  uint8_t                   ob[BQ_BUFFER_SIZE(SERIAL_USB_BUFFERS_TX_NUMBER, \
+                                              SERIAL_USB_BUFFERS_TX_SIZE)]; \
   /* End of the mandatory fields.*/                                         \
   /* Current configuration data.*/                                          \
   const SerialUSBConfig     *config;
diff --git a/os/hal/ports/STM32/LLD/OTGv1/hal_usb_lld.c b/os/hal/ports/STM32/LLD/OTGv1/hal_usb_lld.c
index 76f7c320b..13480956c 100644
--- a/os/hal/ports/STM32/LLD/OTGv1/hal_usb_lld.c
+++ b/os/hal/ports/STM32/LLD/OTGv1/hal_usb_lld.c
@@ -521,6 +521,12 @@ static void otg_isoc_out_failed_handler(USBDriver *usbp) {
   }
 }
 
+
+/* IRQ flags which will trigger a retry around the IRQ loop */
+#define IRQ_RETRY_MASK (GINTSTS_NPTXFE | \
+      GINTSTS_PTXFE |  \
+      GINTSTS_RXFLVL)
+
 /**
  * @brief   OTG shared ISR.
  *
@@ -531,7 +537,9 @@ static void otg_isoc_out_failed_handler(USBDriver *usbp) {
 static void usb_lld_serve_interrupt(USBDriver *usbp) {
   stm32_otg_t *otgp = usbp->otg;
   uint32_t sts, src;
+  int retry_count = 8;
 
+irq_retry:
   sts  = otgp->GINTSTS;
   sts &= otgp->GINTMSK;
   otgp->GINTSTS = sts;
@@ -603,8 +611,12 @@ static void usb_lld_serve_interrupt(USBDriver *usbp) {
     otg_rxfifo_handler(usbp);
   }
 
+  src = 0;
   /* IN/OUT endpoints event handling.*/
-  src = otgp->DAINT;
+  if (sts & (GINTSTS_OEPINT | GINTSTS_IEPINT)) {
+    src = otgp->DAINT;
+  }
+
   if (sts & GINTSTS_OEPINT) {
     if (src & (1 << 16))
       otg_epout_handler(usbp, 0);
@@ -665,6 +677,14 @@ static void usb_lld_serve_interrupt(USBDriver *usbp) {
       otg_epin_handler(usbp, 8);
 #endif
   }
+
+  /*
+   * if we've had fifo events, we should try and go around the
+   * loop again to see if there's any point in returning yet.
+   */
+
+  if (sts & IRQ_RETRY_MASK && --retry_count > 0)
+    goto irq_retry;
 }
 
 /*===========================================================================*/
diff --git a/os/hal/src/hal_serial_usb.c b/os/hal/src/hal_serial_usb.c
index 9de5dd888..526c4eaf0 100644
--- a/os/hal/src/hal_serial_usb.c
+++ b/os/hal/src/hal_serial_usb.c
@@ -73,7 +73,7 @@ static bool sdu_start_receive(SerialUSBDriver *sdup) {
 
   /* Buffer found, starting a new transaction.*/
   usbStartReceiveI(sdup->config->usbp, sdup->config->bulk_out,
-                   buf, SERIAL_USB_BUFFERS_SIZE);
+                   buf, SERIAL_USB_BUFFERS_RX_SIZE);
 
   return false;
 }
@@ -225,10 +225,10 @@ void sduObjectInit(SerialUSBDriver *sdup) {
   osalEventObjectInit(&sdup->event);
   sdup->state = SDU_STOP;
   ibqObjectInit(&sdup->ibqueue, true, sdup->ib,
-                SERIAL_USB_BUFFERS_SIZE, SERIAL_USB_BUFFERS_NUMBER,
+                SERIAL_USB_BUFFERS_RX_SIZE, SERIAL_USB_BUFFERS_RX_NUMBER,
                 ibnotify, sdup);
   obqObjectInit(&sdup->obqueue, true, sdup->ob,
-                SERIAL_USB_BUFFERS_SIZE, SERIAL_USB_BUFFERS_NUMBER,
+                SERIAL_USB_BUFFERS_TX_SIZE, SERIAL_USB_BUFFERS_TX_NUMBER,
                 obnotify, sdup);
 }
 
diff --git a/testhal/AT32/AT32F4xx/ADC/halconf.h b/testhal/AT32/AT32F4xx/ADC/halconf.h
index 97e01635f..9ad29bea5 100644
--- a/testhal/AT32/AT32F4xx/ADC/halconf.h
+++ b/testhal/AT32/AT32F4xx/ADC/halconf.h
@@ -427,7 +427,7 @@
  *          buffers.
  */
 #if !defined(SERIAL_USB_BUFFERS_SIZE) || defined(__DOXYGEN__)
-#define SERIAL_USB_BUFFERS_SIZE             256
+#define SERIAL_USB_BUFFERS_SIZE             64
 #endif
 
 /**
@@ -435,7 +435,7 @@
  * @note    The default is 2 buffers.
  */
 #if !defined(SERIAL_USB_BUFFERS_NUMBER) || defined(__DOXYGEN__)
-#define SERIAL_USB_BUFFERS_NUMBER           2
+#define SERIAL_USB_BUFFERS_NUMBER           8
 #endif
 
 /*===========================================================================*/
diff --git a/testhal/AT32/AT32F4xx/USB_CDC_IAD/halconf.h b/testhal/AT32/AT32F4xx/USB_CDC_IAD/halconf.h
index 7fd4dc3ff..bbd235c43 100644
--- a/testhal/AT32/AT32F4xx/USB_CDC_IAD/halconf.h
+++ b/testhal/AT32/AT32F4xx/USB_CDC_IAD/halconf.h
@@ -450,7 +450,7 @@
  *          buffers.
  */
 #if !defined(SERIAL_USB_BUFFERS_SIZE) || defined(__DOXYGEN__)
-#define SERIAL_USB_BUFFERS_SIZE             256
+#define SERIAL_USB_BUFFERS_SIZE             64
 #endif
 
 /**
@@ -458,7 +458,7 @@
  * @note    The default is 2 buffers.
  */
 #if !defined(SERIAL_USB_BUFFERS_NUMBER) || defined(__DOXYGEN__)
-#define SERIAL_USB_BUFFERS_NUMBER           2
+#define SERIAL_USB_BUFFERS_NUMBER           8
 #endif
 
 /*===========================================================================*/