diff --git a/include/picrin/macro.h b/include/picrin/macro.h
index 1dd6cd81..672feb73 100644
--- a/include/picrin/macro.h
+++ b/include/picrin/macro.h
@@ -18,14 +18,17 @@ struct pic_syntax {
     PIC_STX_LAMBDA,
     PIC_STX_IF,
     PIC_STX_BEGIN,
+    PIC_STX_MACRO,
     PIC_STX_DEFMACRO
   } kind;
   pic_sym sym;
+  struct pic_proc *macro;
 };
 
 #define pic_syntax(v) ((struct pic_syntax *)pic_ptr(v))
 #define pic_syntax_p(v) (pic_type(v) == PIC_TT_SYNTAX)
 
 struct pic_syntax *pic_syntax_new(pic_state *, int kind, pic_sym sym);
+struct pic_syntax *pic_syntax_new_macro(pic_state *, pic_sym, struct pic_proc *);
 
 #endif
diff --git a/src/gc.c b/src/gc.c
index 2264d5bc..c12a1633 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -276,6 +276,11 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
     break;
   }
   case PIC_TT_SYNTAX: {
+    struct pic_syntax *stx = (struct pic_syntax *)obj;
+
+    if (stx->macro) {
+      gc_mark_object(pic, (struct pic_object *)stx->macro);
+    }
     break;
   }
   case PIC_TT_SENV: {
diff --git a/src/macro.c b/src/macro.c
index b379aed0..e4825e39 100644
--- a/src/macro.c
+++ b/src/macro.c
@@ -385,6 +385,19 @@ pic_syntax_new(pic_state *pic, int kind, pic_sym sym)
   stx = (struct pic_syntax *)pic_obj_alloc(pic, sizeof(struct pic_syntax), PIC_TT_SYNTAX);
   stx->kind = kind;
   stx->sym = sym;
+  stx->macro = NULL;
+  return stx;
+}
+
+struct pic_syntax *
+pic_syntax_new_macro(pic_state *pic, pic_sym sym, struct pic_proc *macro)
+{
+  struct pic_syntax *stx;
+
+  stx = (struct pic_syntax *)pic_obj_alloc(pic, sizeof(struct pic_syntax), PIC_TT_SYNTAX);
+  stx->kind = PIC_STX_MACRO;
+  stx->sym = sym;
+  stx->macro = macro;
   return stx;
 }