diff --git a/src/macro.c b/src/macro.c
index eeb050f1..4a9b77be 100644
--- a/src/macro.c
+++ b/src/macro.c
@@ -18,7 +18,7 @@ new_uniq_sym(pic_state *pic, pic_sym base)
   char *str;
   pic_sym uniq;
 
-  str = (char *)pic_alloc(pic, strlen(pic_symbol_name(pic, base)) + (int)log10(s) + 2);
+  str = (char *)pic_alloc(pic, strlen(pic_symbol_name(pic, base)) + (int)log10(s) + 3);
   sprintf(str, "%s@%d", pic_symbol_name(pic, base), s);
   uniq = pic_intern_cstr(pic, str);