1 files changed, 1 insertions, 1 deletions
diff --git a/py/gc.h b/py/gc.h
index fd48d26645..dc276dd2b3 100644
--- a/py/gc.h
+++ b/py/gc.h
@@ -40,7 +40,7 @@ void gc_collect_end(void);
 
 void *gc_alloc(mp_uint_t n_bytes, bool has_finaliser);
 void gc_free(void *ptr);
-mp_uint_t gc_nbytes(void *ptr);
+mp_uint_t gc_nbytes(const void *ptr);
 void *gc_realloc(void *ptr, mp_uint_t n_bytes);
 
 typedef struct _gc_info_t {