diff --git a/ports/litex/boards/fomu/fomu-spi.ld b/ports/litex/boards/fomu/fomu-spi.ld
index 9b6443c673..e7db25b0c5 100644
--- a/ports/litex/boards/fomu/fomu-spi.ld
+++ b/ports/litex/boards/fomu/fomu-spi.ld
@@ -51,6 +51,11 @@ SECTIONS
         *(.text.tu_edpt_dir)
         *(.text.tu_fifo_empty)
         *(.text.usbd_edpt_busy)
+        *(.text.usb_irq_handler)
+        *(.text.supervisor_tick)
+        *(.text.port_get_raw_ticks)
+        *(.text.__modsi3)
+        *(.text.__udivsi3)
         *(.text.irq_getmask)
         *(.text.irq_setmask)
         *(.text.irq_pending)
diff --git a/ports/litex/common-hal/microcontroller/__init__.c b/ports/litex/common-hal/microcontroller/__init__.c
index 3c91661144..522a41e2e3 100644
--- a/ports/litex/common-hal/microcontroller/__init__.c
+++ b/ports/litex/common-hal/microcontroller/__init__.c
@@ -59,12 +59,15 @@ void common_hal_mcu_delay_us(uint32_t delay) {
 
 volatile uint32_t nesting_count = 0;
 
+__attribute__((section(".ramtext")))
 void common_hal_mcu_disable_interrupts(void) {
-    irq_setie(0);
-    // __DMB();
+    if (nesting_count == 0) {
+        irq_setie(0);
+    }
     nesting_count++;
 }
 
+__attribute__((section(".ramtext")))
 void common_hal_mcu_enable_interrupts(void) {
     if (nesting_count == 0) {
         // This is very very bad because it means there was mismatched disable/enables so we
diff --git a/ports/litex/mphalport.c b/ports/litex/mphalport.c
index 862f163939..c7369dc050 100644
--- a/ports/litex/mphalport.c
+++ b/ports/litex/mphalport.c
@@ -44,16 +44,31 @@ void mp_hal_delay_us(mp_uint_t delay) {
 
 extern void SysTick_Handler(void);
 
+// This value contains the number of times "common_hal_mcu_disable_interrupts()"
+// has been called without calling "common_hal_mcu_enable_interrupts()". Since
+// this is the interrupt handler, that means we're handling an interrupt, so
+// this value should be `0`.
+//
+// Interrupts should already be disabled when this handler is running, which means
+// this value is logically already `1`. If we didn't do this, then interrupts would
+// be prematurely enabled by interrupt handlers that enable and disable interrupts.
+extern volatile uint32_t nesting_count;
+
 __attribute__((section(".ramtext")))
 void isr(void) {
     uint8_t irqs = irq_pending() & irq_getmask();
 
+    // Increase the "nesting count". Note: This should be going from 0 -> 1.
+    nesting_count += 1;
 #ifdef CFG_TUSB_MCU
     if (irqs & (1 << USB_INTERRUPT))
         usb_irq_handler();
 #endif
     if (irqs & (1 << TIMER0_INTERRUPT))
         SysTick_Handler();
+
+    // Decrease the "nesting count". Note: This should be going from 1 -> 0.
+    nesting_count -= 1;
 }
 
 mp_uint_t cpu_get_regs_and_sp(mp_uint_t *regs) {
diff --git a/ports/litex/supervisor/port.c b/ports/litex/supervisor/port.c
index 4dea020652..04ff1c09bf 100644
--- a/ports/litex/supervisor/port.c
+++ b/ports/litex/supervisor/port.c
@@ -32,6 +32,8 @@
 #include "irq.h"
 #include "csr.h"
 
+#include "shared-bindings/microcontroller/__init__.h"
+
 // Global millisecond tick count. 1024 per second because most RTCs are clocked with 32.768khz
 // crystals.
 volatile uint64_t raw_ticks = 0;
@@ -129,9 +131,9 @@ uint32_t port_get_saved_word(void) {
 
 uint64_t port_get_raw_ticks(uint8_t* subticks) {
     // Reading 64 bits may take two loads, so turn of interrupts while we do it.
-    irq_setie(false);
+    common_hal_mcu_disable_interrupts();
     uint64_t raw_tick_snapshot = raw_ticks;
-    irq_setie(true);
+    common_hal_mcu_enable_interrupts();
     return raw_tick_snapshot;
 }