diff --git a/ports/raspberrypi/supervisor/port.c b/ports/raspberrypi/supervisor/port.c
index 1b72592172..213084582b 100644
--- a/ports/raspberrypi/supervisor/port.c
+++ b/ports/raspberrypi/supervisor/port.c
@@ -238,7 +238,7 @@ void port_interrupt_after_ticks(uint32_t ticks) {
 void port_idle_until_interrupt(void) {
     common_hal_mcu_disable_interrupts();
     if (!background_callback_pending()) {
-        asm volatile ("dsb 0xF":::"memory");
+        asm volatile ("dsb 0xF" ::: "memory");
         __wfi();
     }
     common_hal_mcu_enable_interrupts();