diff --git a/src/portable/espressif/esp32s2/dcd_esp32s2.c b/src/portable/espressif/esp32s2/dcd_esp32s2.c
index b4d869517..755e06701 100644
--- a/src/portable/espressif/esp32s2/dcd_esp32s2.c
+++ b/src/portable/espressif/esp32s2/dcd_esp32s2.c
@@ -78,7 +78,8 @@ static xfer_ctl_t xfer_status[EP_MAX][2];
 static uint8_t _allocated_fifos = 1; //FIFO0 is always in use
 
 // Will either return an unused FIFO number, or 0 if all are used.
-static uint8_t get_free_fifo(){
+static uint8_t get_free_fifo(void)
+{
   if (_allocated_fifos < EP_FIFO_NUM) return _allocated_fifos++;
   return 0;
 }
diff --git a/src/portable/st/synopsys/dcd_synopsys.c b/src/portable/st/synopsys/dcd_synopsys.c
index 7eb63e52f..03c33c598 100644
--- a/src/portable/st/synopsys/dcd_synopsys.c
+++ b/src/portable/st/synopsys/dcd_synopsys.c
@@ -231,6 +231,7 @@ static void bus_reset(uint8_t rhport)
 }
 
 // Set turn-around timeout according to link speed
+extern uint32_t SystemCoreClock;
 static void set_turnaround(USB_OTG_GlobalTypeDef * usb_otg, tusb_speed_t speed)
 {
   usb_otg->GUSBCFG &= ~USB_OTG_GUSBCFG_TRDT;
@@ -243,7 +244,6 @@ static void set_turnaround(USB_OTG_GlobalTypeDef * usb_otg, tusb_speed_t speed)
   else
   {
     // Turnaround timeout depends on the MCU clock
-    extern uint32_t SystemCoreClock;
     uint32_t turnaround;
 
     if ( SystemCoreClock >= 32000000U )