diff --git a/src/gc.c b/src/gc.c
index fe6e2176..d0fbf1e3 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -268,7 +268,7 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
       gc_mark_object(pic, (struct pic_object *)stx->macro);
     }
     if (stx->senv) {
-      gc_mark_object(pic, (struct pic_object *)stx->macro);
+      gc_mark_object(pic, (struct pic_object *)stx->senv);
     }
     break;
   }