diff --git a/ports/rp2/main.c b/ports/rp2/main.c
index 570c4302f0..afc22aee72 100644
--- a/ports/rp2/main.c
+++ b/ports/rp2/main.c
@@ -59,16 +59,8 @@
 #include "lib/cyw43-driver/src/cyw43.h"
 #endif
 
-#ifndef MICROPY_GC_HEAP_SIZE
-#if MICROPY_PY_LWIP
-#define MICROPY_GC_HEAP_SIZE 166 * 1024
-#else
-#define MICROPY_GC_HEAP_SIZE 192 * 1024
-#endif
-#endif
-
 extern uint8_t __StackTop, __StackBottom;
-__attribute__((section(".uninitialized_bss"))) static char gc_heap[MICROPY_GC_HEAP_SIZE];
+extern uint8_t __GcHeapStart, __GcHeapEnd;
 
 // Embed version info in the binary in machine readable form
 bi_decl(bi_program_version_string(MICROPY_GIT_TAG));
@@ -118,7 +110,7 @@ int main(int argc, char **argv) {
     // Initialise stack extents and GC heap.
     mp_stack_set_top(&__StackTop);
     mp_stack_set_limit(&__StackTop - &__StackBottom - 256);
-    gc_init(&gc_heap[0], &gc_heap[MP_ARRAY_SIZE(gc_heap)]);
+    gc_init(&__GcHeapStart, &__GcHeapEnd);
 
     #if MICROPY_PY_LWIP
     // lwIP doesn't allow to reinitialise itself by subsequent calls to this function
diff --git a/ports/rp2/memmap_mp.ld b/ports/rp2/memmap_mp.ld
index 82f9cb01c3..6be05b094f 100644
--- a/ports/rp2/memmap_mp.ld
+++ b/ports/rp2/memmap_mp.ld
@@ -248,11 +248,18 @@ SECTIONS
     __StackTop = ORIGIN(SCRATCH_Y) + LENGTH(SCRATCH_Y);
     __StackOneBottom = __StackOneTop - SIZEOF(.stack1_dummy);
     __StackBottom = __StackTop - SIZEOF(.stack_dummy);
+    /* Define start and end of GC heap */
+    __GcHeapStart = __bss_end__;
+    __GcHeapEnd   = __StackLimit;
     PROVIDE(__stack = __StackTop);
 
     /* Check if data + heap + stack exceeds RAM limit */
     ASSERT(__StackLimit >= __HeapLimit, "region RAM overflowed")
 
+    /* Check GC heap is at least 128 KB */
+    /* On a RP2040 using all SRAM this should always be the case. */
+    ASSERT((__GcHeapEnd - __GcHeapStart) > 128*1024, "GcHeap is too small")
+
     ASSERT( __binary_info_header_end - __logical_binary_start <= 256, "Binary info must be in first 256 bytes of the binary")
     /* todo assert on extra code */
 }