diff --git a/py/gc.c b/py/gc.c
index 1b99ab4cfa..734f5c3648 100644
--- a/py/gc.c
+++ b/py/gc.c
@@ -289,7 +289,7 @@ STATIC void gc_sweep(void) {
                 }
 #endif
                 free_tail = 1;
-                DEBUG_printf("gc_sweep(%x)\n", PTR_FROM_BLOCK(block));
+                DEBUG_printf("gc_sweep(%p)\n", PTR_FROM_BLOCK(block));
                 #if MICROPY_PY_GC_COLLECT_RETVAL
                 MP_STATE_MEM(gc_collected)++;
                 #endif