diff --git a/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/libraries/README.md b/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/libraries/README.md
index d1fbd84ee1..9a998afc0d 100644
--- a/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/libraries/README.md
+++ b/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/libraries/README.md
@@ -4,6 +4,8 @@ components/libraries
 
 # Modifications
 
+ * Modified util/app_util_platform.c to retarget critical section enter/exit calls to Mbed's HAL API so they both share the same nested critical regions counter. This only applies in builds without `SOFTDEVICE_PRESENT` defined.
+
 Only essential folders have been copied over.
 
 Removed:
diff --git a/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/libraries/util/app_util_platform.c b/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/libraries/util/app_util_platform.c
index 71690d0fdc..af453651ef 100644
--- a/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/libraries/util/app_util_platform.c
+++ b/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/libraries/util/app_util_platform.c
@@ -39,6 +39,8 @@
  */
 #include "app_util_platform.h"
 
+#include "mbed_critical.h"
+
 #ifdef SOFTDEVICE_PRESENT
 /* Global nvic state instance, required by nrf_nvic.h */
 nrf_nvic_state_t nrf_nvic_state;
@@ -71,8 +73,13 @@ void app_util_critical_region_enter(uint8_t *p_nested)
     /* return value can be safely ignored */
     (void) sd_nvic_critical_region_enter(p_nested);
 #else
-    app_util_disable_irq();
+    /** Mbed modification
+     *  Retarget nRF SDK to use Mbed critical section API
+     */
+    //app_util_disable_irq();
+    core_util_critical_section_enter();
 #endif
+
 }
 
 void app_util_critical_region_exit(uint8_t nested)
@@ -85,7 +92,11 @@ void app_util_critical_region_exit(uint8_t nested)
     /* return value can be safely ignored */
     (void) sd_nvic_critical_region_exit(nested);
 #else
-    app_util_enable_irq();
+    /** Mbed modification
+     *  Retarget nRF SDK to use Mbed critical section API
+     */
+    //app_util_enable_irq();
+    core_util_critical_section_exit();
 #endif
 }