diff --git a/src/c/printer/integer_to_string.d b/src/c/printer/integer_to_string.d
index 91225f7fc..8ea4c7351 100644
--- a/src/c/printer/integer_to_string.d
+++ b/src/c/printer/integer_to_string.d
@@ -27,7 +27,7 @@ bignum_to_string(cl_object buffer, cl_object x, cl_object base)
         }
         str_size = mpz_sizeinbase(x->big.big_num, b);
         buffer = _ecl_ensure_buffer(buffer, str_size+1);
-        if (str_size <= 64) {
+        if (str_size <= 63) {
                 char txt[64];
                 mpz_get_str(txt, b, x->big.big_num);
                 _ecl_string_push_c_string(buffer, txt);