diff --git a/stmhal/exti.c b/stmhal/exti.c
index 552efdf080..5ea3db62bb 100644
--- a/stmhal/exti.c
+++ b/stmhal/exti.c
@@ -105,9 +105,12 @@ STATIC const uint8_t nvic_irq_channel[EXTI_NUM_VECTORS] = {
     OTG_HS_WKUP_IRQn, TAMP_STAMP_IRQn, RTC_WKUP_IRQn
 };
 
+// Set override_callback_obj to true if you want to unconditionally set the
+// callback function.
+//
 // NOTE: param is for C callers. Python can use closure to get an object bound
 //       with the function.
-uint exti_register(mp_obj_t pin_obj, mp_obj_t mode_obj, mp_obj_t pull_obj, mp_obj_t callback_obj, void *param) {
+uint exti_register(mp_obj_t pin_obj, mp_obj_t mode_obj, mp_obj_t pull_obj, mp_obj_t callback_obj, bool override_callback_obj, void *param) {
     const pin_obj_t *pin = NULL;
     uint v_line;
 
@@ -143,7 +146,7 @@ uint exti_register(mp_obj_t pin_obj, mp_obj_t mode_obj, mp_obj_t pull_obj, mp_ob
     }
 
     exti_vector_t *v = &exti_vector[v_line];
-    if (v->callback_obj != mp_const_none && callback_obj != mp_const_none) {
+    if (!override_callback_obj && v->callback_obj != mp_const_none && callback_obj != mp_const_none) {
         nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "EXTI vector %d is already in use", v_line));
     }
 
@@ -272,7 +275,7 @@ STATIC mp_obj_t exti_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp
     mp_obj_t mode_obj = args[1];
     mp_obj_t trigger_obj = args[2];
     mp_obj_t callback_obj = args[3];
-    self->line = exti_register(line_obj, mode_obj, trigger_obj, callback_obj, NULL);
+    self->line = exti_register(line_obj, mode_obj, trigger_obj, callback_obj, false, NULL);
 
     return self;
 }
@@ -315,7 +318,8 @@ void Handle_EXTI_Irq(uint32_t line) {
                 } else {
                     // Uncaught exception; disable the callback so it doesn't run again.
                     v->callback_obj = mp_const_none;
-                    printf("Uncaught exception in EXTI interrupt handler on line %lu\n", line);
+                    exti_disable(line);
+                    printf("Uncaught exception in EXTI interrupt handler line %lu\n", line);
                     mp_obj_print_exception((mp_obj_t)nlr.ret_val);
                 }
                 gc_unlock();
diff --git a/stmhal/exti.h b/stmhal/exti.h
index a6b50b26e8..6feb9dceaf 100644
--- a/stmhal/exti.h
+++ b/stmhal/exti.h
@@ -22,7 +22,7 @@
 
 void exti_init(void);
 
-uint exti_register(mp_obj_t pin_obj, mp_obj_t mode_obj, mp_obj_t trigger_obj, mp_obj_t callback_obj, void *param);
+uint exti_register(mp_obj_t pin_obj, mp_obj_t mode_obj, mp_obj_t trigger_obj, mp_obj_t callback_obj, bool override_callback_obj, void *param);
 
 void exti_enable(uint line);
 void exti_disable(uint line);
diff --git a/stmhal/usrsw.c b/stmhal/usrsw.c
index 453c3dfa82..5133392ccd 100644
--- a/stmhal/usrsw.c
+++ b/stmhal/usrsw.c
@@ -49,14 +49,9 @@ void switch_init0(void) {
     HAL_GPIO_Init(MICROPY_HW_USRSW_PIN.gpio, &init);
 }
 
-// this function inits the callback and EXTI function of the switch
+// this function inits the callback pointer
 void switch_init(void) {
     switch_user_callback_obj = mp_const_none;
-    exti_register((mp_obj_t)&MICROPY_HW_USRSW_PIN,
-                  MP_OBJ_NEW_SMALL_INT(MICROPY_HW_USRSW_EXTI_MODE),
-                  MP_OBJ_NEW_SMALL_INT(MICROPY_HW_USRSW_PULL),
-                  (mp_obj_t)&switch_callback_obj,
-                  NULL);
 }
 
 int switch_get(void) {
@@ -70,9 +65,19 @@ int switch_get(void) {
 static mp_obj_t pyb_switch(uint n_args, mp_obj_t *args) {
     if (n_args == 0) {
         return switch_get() ? mp_const_true : mp_const_false;
+    } else {
+        switch_user_callback_obj = args[0];
+        // Init the EXTI each time this function is called, since the EXTI
+        // may have been disabled by an exception in the interrupt, or the
+        // user disabling the line explicitly.
+        exti_register((mp_obj_t)&MICROPY_HW_USRSW_PIN,
+                      MP_OBJ_NEW_SMALL_INT(MICROPY_HW_USRSW_EXTI_MODE),
+                      MP_OBJ_NEW_SMALL_INT(MICROPY_HW_USRSW_PULL),
+                      switch_user_callback_obj == mp_const_none ? mp_const_none : (mp_obj_t)&switch_callback_obj,
+                      true,
+                      NULL);
+        return mp_const_none;
     }
-    switch_user_callback_obj = args[0];
-    return mp_const_none;
 }
 
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_switch_obj, 0, 1, pyb_switch);