diff --git a/TESTS/mbedmicro-rtos-mbed/basic/main.cpp b/TESTS/mbedmicro-rtos-mbed/basic/main.cpp
index 8c115c38f7b..a696020b45d 100644
--- a/TESTS/mbedmicro-rtos-mbed/basic/main.cpp
+++ b/TESTS/mbedmicro-rtos-mbed/basic/main.cpp
@@ -24,7 +24,7 @@
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
 #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822) || defined(TARGET_MCU_NRF52832)
-#define STACK_SIZE 512
+#define STACK_SIZE 768
 #else
 #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/TESTS/mbedmicro-rtos-mbed/isr/main.cpp b/TESTS/mbedmicro-rtos-mbed/isr/main.cpp
index d34a38fb444..92064d567ca 100644
--- a/TESTS/mbedmicro-rtos-mbed/isr/main.cpp
+++ b/TESTS/mbedmicro-rtos-mbed/isr/main.cpp
@@ -27,7 +27,7 @@
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822) || defined(TARGET_MCU_NRF52832)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/TESTS/mbedmicro-rtos-mbed/mail/main.cpp b/TESTS/mbedmicro-rtos-mbed/mail/main.cpp
index d276d575473..3f9523513e9 100644
--- a/TESTS/mbedmicro-rtos-mbed/mail/main.cpp
+++ b/TESTS/mbedmicro-rtos-mbed/mail/main.cpp
@@ -35,7 +35,7 @@ typedef struct {
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822) || defined(TARGET_MCU_NRF52832)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/TESTS/mbedmicro-rtos-mbed/mutex/main.cpp b/TESTS/mbedmicro-rtos-mbed/mutex/main.cpp
index 6dec6865336..f8da3c15bf2 100644
--- a/TESTS/mbedmicro-rtos-mbed/mutex/main.cpp
+++ b/TESTS/mbedmicro-rtos-mbed/mutex/main.cpp
@@ -37,7 +37,7 @@
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822) || defined(TARGET_MCU_NRF52832)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 1024
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/TESTS/mbedmicro-rtos-mbed/queue/main.cpp b/TESTS/mbedmicro-rtos-mbed/queue/main.cpp
index d6a124348a2..f4aca165db0 100644
--- a/TESTS/mbedmicro-rtos-mbed/queue/main.cpp
+++ b/TESTS/mbedmicro-rtos-mbed/queue/main.cpp
@@ -35,7 +35,7 @@ typedef struct {
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822) || defined(TARGET_MCU_NRF52832)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/TESTS/mbedmicro-rtos-mbed/semaphore/main.cpp b/TESTS/mbedmicro-rtos-mbed/semaphore/main.cpp
index 8fe120d2a35..7d625d59fe2 100644
--- a/TESTS/mbedmicro-rtos-mbed/semaphore/main.cpp
+++ b/TESTS/mbedmicro-rtos-mbed/semaphore/main.cpp
@@ -40,7 +40,7 @@
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822) || defined(TARGET_MCU_NRF52832)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/TESTS/mbedmicro-rtos-mbed/signals/main.cpp b/TESTS/mbedmicro-rtos-mbed/signals/main.cpp
index 3fd784034d1..b8c385156f0 100644
--- a/TESTS/mbedmicro-rtos-mbed/signals/main.cpp
+++ b/TESTS/mbedmicro-rtos-mbed/signals/main.cpp
@@ -26,7 +26,7 @@ const int SIGNAL_HANDLE_DELEY = 25;
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822) || defined(TARGET_MCU_NRF52832)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/hal/targets.json b/hal/targets.json
index 62050d8a934..d3949b1fede 100644
--- a/hal/targets.json
+++ b/hal/targets.json
@@ -1195,14 +1195,14 @@
             "toolchains": ["ARM_STD", "GCC_ARM"]
         },
         "program_cycle_s": 6,
-        "default_build": "small",
         "features": ["BLE"]
     },
     "MCU_NRF51_16K_BASE": {
         "inherits": ["MCU_NRF51"],
         "extra_labels_add": ["MCU_NORDIC_16K", "MCU_NRF51_16K"],
         "macros_add": ["TARGET_MCU_NORDIC_16K", "TARGET_MCU_NRF51_16K"],
-        "public": false
+        "public": false,
+        "default_build": "small"
     },
     "MCU_NRF51_16K_BOOT_BASE": {
         "inherits": ["MCU_NRF51_16K_BASE"],
@@ -1860,7 +1860,6 @@
             "toolchains": ["ARM_STD", "GCC_ARM", "IAR"]
         },
         "program_cycle_s": 6,
-        "default_build": "small",
         "features": ["BLE"],
         "config":{
             "lf_clock_src": {
@@ -1912,8 +1911,7 @@
                 "value": "NRF_LF_SRC_XTAL",
                 "macro_name": "MBED_CONF_NORDIC_NRF_LF_CLOCK_SRC"
             }
-        },
-        "default_build": "small"
+        }
     },
     "NRF52_DK": {
         "supported_form_factors": ["ARDUINO"],
diff --git a/libraries/tests/rtos/mbed/basic/main.cpp b/libraries/tests/rtos/mbed/basic/main.cpp
index 038cf05b6ac..d3de4f6a36f 100644
--- a/libraries/tests/rtos/mbed/basic/main.cpp
+++ b/libraries/tests/rtos/mbed/basic/main.cpp
@@ -24,7 +24,7 @@
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/libraries/tests/rtos/mbed/isr/main.cpp b/libraries/tests/rtos/mbed/isr/main.cpp
index ae27fa6b8f3..15e91b8b02b 100644
--- a/libraries/tests/rtos/mbed/isr/main.cpp
+++ b/libraries/tests/rtos/mbed/isr/main.cpp
@@ -27,7 +27,7 @@
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/libraries/tests/rtos/mbed/mail/main.cpp b/libraries/tests/rtos/mbed/mail/main.cpp
index d609afadcd8..caed3b2dc2a 100644
--- a/libraries/tests/rtos/mbed/mail/main.cpp
+++ b/libraries/tests/rtos/mbed/mail/main.cpp
@@ -35,7 +35,7 @@ typedef struct {
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/libraries/tests/rtos/mbed/mutex/main.cpp b/libraries/tests/rtos/mbed/mutex/main.cpp
index 4d77f47f701..20aed9c2281 100644
--- a/libraries/tests/rtos/mbed/mutex/main.cpp
+++ b/libraries/tests/rtos/mbed/mutex/main.cpp
@@ -37,7 +37,7 @@
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/libraries/tests/rtos/mbed/queue/main.cpp b/libraries/tests/rtos/mbed/queue/main.cpp
index 2a44e84b2d3..7dd8b50edfc 100644
--- a/libraries/tests/rtos/mbed/queue/main.cpp
+++ b/libraries/tests/rtos/mbed/queue/main.cpp
@@ -35,7 +35,7 @@ typedef struct {
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/libraries/tests/rtos/mbed/semaphore/main.cpp b/libraries/tests/rtos/mbed/semaphore/main.cpp
index 2c38d453af0..63b8121baf2 100644
--- a/libraries/tests/rtos/mbed/semaphore/main.cpp
+++ b/libraries/tests/rtos/mbed/semaphore/main.cpp
@@ -40,7 +40,7 @@
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif
diff --git a/libraries/tests/rtos/mbed/signals/main.cpp b/libraries/tests/rtos/mbed/signals/main.cpp
index bbbe1cd70ee..65b3ce038a2 100644
--- a/libraries/tests/rtos/mbed/signals/main.cpp
+++ b/libraries/tests/rtos/mbed/signals/main.cpp
@@ -26,7 +26,7 @@
 #elif (defined(TARGET_EFM32GG_STK3700)) && !defined(TOOLCHAIN_ARM_MICRO)
     #define STACK_SIZE 1536
 #elif defined(TARGET_MCU_NRF51822)
-    #define STACK_SIZE 512
+    #define STACK_SIZE 768
 #else
     #define STACK_SIZE DEFAULT_STACK_SIZE
 #endif