diff --git a/gc.c b/gc.c
index bcc3f87642..ed05c3f3e4 100644
--- a/gc.c
+++ b/gc.c
@@ -9215,9 +9215,9 @@ rb_gc_register_address(VALUE *addr)
      */
     RB_GC_GUARD(obj);
     if (0 && !SPECIAL_CONST_P(obj)) {
-	rb_warn("Object is assigned to registering address already: %"PRIsVALUE,
-		rb_obj_class(obj));
-	rb_print_backtrace();
+        rb_warn("Object is assigned to registering address already: %"PRIsVALUE,
+                rb_obj_class(obj));
+        rb_print_backtrace();
     }
 }