diff --git a/include/picrin.h b/include/picrin.h
index ea107174..ebf43a7b 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -57,7 +57,8 @@ typedef struct {
   pic_value *globals;
   size_t glen, gcapa;
 
-  struct pic_senv *global_senv;
+  pic_value lib_tbl;
+  struct pic_lib *lib;
 
   struct pic_irep **irep;
   size_t ilen, icapa;
diff --git a/src/gc.c b/src/gc.c
index b2cd56a0..4c6ac3f0 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -463,15 +463,13 @@ gc_mark_phase(pic_state *pic)
     gc_mark(pic, pic->globals[i]);
   }
 
-  /* macros */
-  if (pic->global_senv) {
-    gc_mark_object(pic, (struct pic_object *)pic->global_senv);
-  }
-
   /* pool */
   for (i = 0; i < pic->plen; ++i) {
     gc_mark(pic, pic->pool[i]);
   }
+
+  /* library table */
+  gc_mark(pic, pic->lib_tbl);
 }
 
 static void
diff --git a/src/macro.c b/src/macro.c
index e750d9a3..b64a263f 100644
--- a/src/macro.c
+++ b/src/macro.c
@@ -7,6 +7,7 @@
 #include "picrin/pair.h"
 #include "picrin/proc.h"
 #include "picrin/macro.h"
+#include "picrin/lib.h"
 #include "xhash/xhash.h"
 
 #define FALLTHROUGH ((void)0)
@@ -65,7 +66,7 @@ pic_core_syntactic_env(pic_state *pic)
 static struct pic_senv *
 new_global_senv(pic_state *pic)
 {
-  return pic->global_senv;
+  return pic->lib->senv;
 }
 
 static struct pic_senv *
@@ -160,17 +161,18 @@ static void
 pic_defsyntax(pic_state *pic, const char *name, struct pic_proc *macro, struct pic_senv *mac_env)
 {
   struct pic_syntax *stx;
+  struct pic_senv *global_senv = pic->lib->senv;
   int idx;
 
   stx = pic_syntax_new_macro(pic, pic_intern_cstr(pic, name), macro, mac_env);
 
-  idx = pic->global_senv->xlen;
-  if (idx >= pic->global_senv->xcapa) {
+  idx = global_senv->xlen;
+  if (idx >= global_senv->xcapa) {
     pic_abort(pic, "macro table overflow");
   }
-  pic->global_senv->stx[idx] = stx;
-  xh_put(pic->global_senv->tbl, name, ~idx);
-  pic->global_senv->xlen++;
+  global_senv->stx[idx] = stx;
+  xh_put(global_senv->tbl, name, ~idx);
+  global_senv->xlen++;
 }
 
 void
diff --git a/src/state.c b/src/state.c
index cc65d132..18e7b5c7 100644
--- a/src/state.c
+++ b/src/state.c
@@ -65,9 +65,9 @@ pic_open(int argc, char *argv[], char **envp)
   pic->glen = 0;
   pic->gcapa = PIC_GLOBALS_SIZE;
 
-  /* syntactic env */
-  pic->global_senv = NULL;      /* prevent gc from hanging during marking phase */
-  pic->global_senv = pic_core_syntactic_env(pic);
+  /* libraries */
+  pic->lib_tbl = pic_nil_value();
+  pic->lib = NULL;
 
   /* pool */
   pic->pool = (pic_value *)calloc(PIC_POOL_SIZE, sizeof(pic_value));