diff --git a/ports/unix/alloc.c b/ports/unix/alloc.c
index 7fe7b4dba4..e9cf521583 100644
--- a/ports/unix/alloc.c
+++ b/ports/unix/alloc.c
@@ -104,4 +104,6 @@ void ffi_closure_free(void *ptr) {
 }
 #endif
 
+MP_REGISTER_ROOT_POINTER(void *mmap_region_head);
+
 #endif // MICROPY_EMIT_NATIVE || (MICROPY_PY_FFI && MICROPY_FORCE_PLAT_ALLOC_EXEC)
diff --git a/ports/unix/mpconfigport.h b/ports/unix/mpconfigport.h
index 4594b8be9d..eb2da23938 100644
--- a/ports/unix/mpconfigport.h
+++ b/ports/unix/mpconfigport.h
@@ -305,7 +305,6 @@ struct _mp_bluetooth_nimble_malloc_t;
 #endif
 
 #define MICROPY_PORT_ROOT_POINTERS \
-    void *mmap_region_head; \
     MICROPY_BLUETOOTH_ROOT_POINTERS \
 
 // We need to provide a declaration/definition of alloca()