diff --git a/hal/common/rtc_time.c b/hal/common/rtc_time.c
index 98227974696..45499379158 100644
--- a/hal/common/rtc_time.c
+++ b/hal/common/rtc_time.c
@@ -16,6 +16,7 @@
 #include "rtc_api.h"
 
 #include <time.h>
+#include "critical.h"
 #include "rtc_time.h"
 #include "us_ticker_api.h"
 
@@ -74,12 +75,12 @@ clock_t clock() {
 }
 
 void attach_rtc(time_t (*read_rtc)(void), void (*write_rtc)(time_t), void (*init_rtc)(void), int (*isenabled_rtc)(void)) {
-    __disable_irq();
+    core_util_critical_section_enter();
     _rtc_read = read_rtc;
     _rtc_write = write_rtc;
     _rtc_init = init_rtc;
     _rtc_isenabled = isenabled_rtc;
-    __enable_irq();
+    core_util_critical_section_exit();
 }
 
 
diff --git a/hal/common/ticker_api.c b/hal/common/ticker_api.c
index 52b48888f6c..e4bf86dcd0c 100644
--- a/hal/common/ticker_api.c
+++ b/hal/common/ticker_api.c
@@ -15,7 +15,7 @@
  */
 #include <stddef.h>
 #include "ticker_api.h"
-#include "cmsis.h"
+#include "critical.h"
 
 void ticker_set_handler(const ticker_data_t *const data, ticker_event_handler handler) {
     data->interface->init();
@@ -55,7 +55,7 @@ void ticker_irq_handler(const ticker_data_t *const data) {
 
 void ticker_insert_event(const ticker_data_t *const data, ticker_event_t *obj, timestamp_t timestamp, uint32_t id) {
     /* disable interrupts for the duration of the function */
-    __disable_irq();
+    core_util_critical_section_enter();
 
     // initialise our data
     obj->timestamp = timestamp;
@@ -84,11 +84,11 @@ void ticker_insert_event(const ticker_data_t *const data, ticker_event_t *obj, t
     /* if we're at the end p will be NULL, which is correct */
     obj->next = p;
 
-    __enable_irq();
+    core_util_critical_section_exit();
 }
 
 void ticker_remove_event(const ticker_data_t *const data, ticker_event_t *obj) {
-    __disable_irq();
+    core_util_critical_section_enter();
 
     // remove this object from the list
     if (data->queue->head == obj) {
@@ -111,7 +111,7 @@ void ticker_remove_event(const ticker_data_t *const data, ticker_event_t *obj) {
         }
     }
 
-    __enable_irq();
+    core_util_critical_section_exit();
 }
 
 timestamp_t ticker_read(const ticker_data_t *const data)
@@ -124,12 +124,12 @@ int ticker_get_next_timestamp(const ticker_data_t *const data, timestamp_t *time
     int ret = 0;
 
     /* if head is NULL, there are no pending events */
-    __disable_irq();
+    core_util_critical_section_enter();
     if (data->queue->head != NULL) {
         *timestamp = data->queue->head->timestamp;
         ret = 1;
     }
-    __enable_irq();
+    core_util_critical_section_exit();
 
     return ret;
 }