diff --git a/include/picrin.h b/include/picrin.h
index 2bf9f9fd..e6846994 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -127,6 +127,13 @@ void pic_gc_run(pic_state *);
 pic_value pic_gc_protect(pic_state *, pic_value);
 size_t pic_gc_arena_preserve(pic_state *);
 void pic_gc_arena_restore(pic_state *, size_t);
+#define pic_void(exec)                          \
+  pic_void_(GENSYM(ai), exec)
+#define pic_void_(ai,exec) do {                 \
+    size_t ai = pic_gc_arena_preserve(pic);     \
+    exec;                                       \
+    pic_gc_arena_restore(pic, ai);              \
+  } while (0)
 
 pic_state *pic_open(int argc, char *argv[], char **envp);
 void pic_close(pic_state *);
diff --git a/src/macro.c b/src/macro.c
index 683c429b..1328581f 100644
--- a/src/macro.c
+++ b/src/macro.c
@@ -204,17 +204,13 @@ macroexpand_deflibrary(pic_state *pic, pic_value expr)
     pic_in_library(pic, pic_cadr(pic, expr));
 
     pic_for_each (v, pic_cddr(pic, expr)) {
-      size_t ai = pic_gc_arena_preserve(pic);
-
-      pic_eval(pic, v);
-
-      pic_gc_arena_restore(pic, ai);
+      pic_void(pic_eval(pic, v));
     }
 
     pic_in_library(pic, prev->name);
   }
   pic_catch {
-    pic_in_library(pic, prev->name);    /* restores pic->lib even if an error occurs */
+    pic_in_library(pic, prev->name); /* restores pic->lib even if an error occurs */
     pic_throw_error(pic, pic->err);
   }