diff --git a/include/picrin.h b/include/picrin.h
index 7588ec61..b9a2190a 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -50,6 +50,7 @@ typedef struct {
   struct xhash *sym_tbl;
   const char **sym_pool;
   size_t slen, scapa;
+  int uniq_sym_count;
 
   /* positive for variables, negative for macros (bitwise-not) */
   struct xhash *global_tbl;
diff --git a/src/macro.c b/src/macro.c
index ff716c42..f3d0262b 100644
--- a/src/macro.c
+++ b/src/macro.c
@@ -1,5 +1,7 @@
 #include <stdio.h>
 #include <assert.h>
+#include <string.h>
+#include <math.h>
 
 #include "picrin.h"
 #include "picrin/pair.h"
@@ -190,3 +192,18 @@ pic_macroexpand(pic_state *pic, pic_value obj)
 
   return v;
 }
+
+static pic_sym
+new_uniq_sym(pic_state *pic, pic_sym base)
+{
+  int s = pic->uniq_sym_count++;
+  char *str;
+  pic_sym uniq;
+
+  str = (char *)pic_alloc(pic, strlen(pic_symbol_name(pic, base)), + (int)log10(s) + 2);
+  sprintf(str, "%s@%d", pic_symbol_name(pic, base), s);
+  uniq = pic_intern_cstr(pic, str);
+
+  pic_free(pic, str);
+  return uniq;
+}
diff --git a/src/state.c b/src/state.c
index d8db2f75..ea212174 100644
--- a/src/state.c
+++ b/src/state.c
@@ -51,6 +51,7 @@ pic_open(int argc, char *argv[], char **envp)
   pic->sym_pool = (const char **)calloc(PIC_SYM_POOL_SIZE, sizeof(const char *));
   pic->slen = 0;
   pic->scapa = pic->slen + PIC_SYM_POOL_SIZE;
+  pic->uniq_sym_count = 0;
 
   /* irep */
   pic->irep = (struct pic_irep **)calloc(PIC_IREP_SIZE, sizeof(struct pic_irep *));