diff --git a/ports/cxd56/configs/circuitpython/defconfig b/ports/cxd56/configs/circuitpython/defconfig
index 268f7a68e9..a97f821dfa 100644
--- a/ports/cxd56/configs/circuitpython/defconfig
+++ b/ports/cxd56/configs/circuitpython/defconfig
@@ -165,7 +165,6 @@ CONFIG_USBDEV=y
 CONFIG_USBDEV_DMA=y
 CONFIG_USBDEV_DUALSPEED=y
 CONFIG_USEC_PER_TICK=1000
-CONFIG_USERMAIN_STACKSIZE=1064960
 CONFIG_USER_ENTRYPOINT="spresense_main"
 CONFIG_VIDEO_ISX012=y
 CONFIG_VIDEO_STREAM=y
diff --git a/ports/cxd56/mpconfigport.h b/ports/cxd56/mpconfigport.h
index df87946b95..27c82337bc 100644
--- a/ports/cxd56/mpconfigport.h
+++ b/ports/cxd56/mpconfigport.h
@@ -27,13 +27,15 @@
 #ifndef __INCLUDED_MPCONFIGPORT_H
 #define __INCLUDED_MPCONFIGPORT_H
 
-#define MICROPY_PY_SYS_PLATFORM "CXD56"
+#define MICROPY_PY_SYS_PLATFORM                 "CXD56"
 
 // 64kiB stack
-#define CIRCUITPY_DEFAULT_STACK_SIZE            0x10000
+#define CIRCUITPY_DEFAULT_STACK_SIZE            (0x10000)
 
 #include "py/circuitpy_mpconfig.h"
 
+#define MICROPY_BYTES_PER_GC_BLOCK              (32)
+
 #define MICROPY_PORT_ROOT_POINTERS \
     CIRCUITPY_COMMON_ROOT_POINTERS \
 
diff --git a/ports/cxd56/spresense-exported-sdk b/ports/cxd56/spresense-exported-sdk
index c991d439fa..752c4cd56d 160000
--- a/ports/cxd56/spresense-exported-sdk
+++ b/ports/cxd56/spresense-exported-sdk
@@ -1 +1 @@
-Subproject commit c991d439fac9c23cfcac0da16fe8055f818d40a4
+Subproject commit 752c4cd56dd0a270a559c28272ceb61ddcb7806c
diff --git a/ports/cxd56/supervisor/port.c b/ports/cxd56/supervisor/port.c
index 7038ca4782..6a32dc0f9e 100644
--- a/ports/cxd56/supervisor/port.c
+++ b/ports/cxd56/supervisor/port.c
@@ -46,12 +46,20 @@
 #include "common-hal/pwmio/PWMOut.h"
 #include "common-hal/busio/UART.h"
 
+#define HEAP_SIZE (1000 * 1024)
+
+uint32_t* heap;
+uint32_t heap_size;
+
 safe_mode_t port_init(void) {
     boardctl(BOARDIOC_INIT, 0);
 
     // Wait until RTC is available
     while (g_rtc_enabled == false);
 
+    heap = memalign(32, HEAP_SIZE);
+    heap_size = HEAP_SIZE / sizeof(uint32_t);
+
     if (board_requests_safe_mode()) {
         return USER_SAFE_MODE;
     }
@@ -100,11 +108,11 @@ uint32_t *port_stack_get_top(void) {
 }
 
 uint32_t *port_heap_get_bottom(void) {
-    return port_stack_get_limit();
+    return heap;
 }
 
 uint32_t *port_heap_get_top(void) {
-    return port_stack_get_top();
+    return heap + heap_size;
 }
 
 extern uint32_t _ebss;