diff --git a/mrbgems/mruby-bigint/core/bigint.c b/mrbgems/mruby-bigint/core/bigint.c
index 7b42c3935..40d59eb38 100644
--- a/mrbgems/mruby-bigint/core/bigint.c
+++ b/mrbgems/mruby-bigint/core/bigint.c
@@ -688,15 +688,16 @@ mpz_get_str(mrb_state *mrb, char *s, mrb_int sz, mrb_int base, mpz_t *x)
   char *se = s+sz;
   int xlen = digits(x);
   mp_limb *t = (mp_limb*)mrb_malloc(mrb, xlen*sizeof(mp_limb));
+  mp_limb *tend = t + xlen;
   memcpy(t, x->p, xlen*sizeof(mp_limb));
   mp_limb b2 = base;
-  const int blim = (sizeof(mp_limb)==sizeof(int))?(base<=10?4:3):(base<=10?9:5);
+  const int blim = (sizeof(mp_limb)==4)?(base<=10?4:3):(base<=10?9:5);
   for (int i=1; i<blim; i++) {
     b2 *= base;
   }
 
   for (;;) {
-    mp_limb *d = t + xlen;
+    mp_limb *d = tend;
     mp_limb a = 0;
     while (--d >= t) {
       mp_limb d0 = *d, d1;
@@ -720,14 +721,14 @@ mpz_get_str(mrb_state *mrb, char *s, mrb_int sz, mrb_int base, mpz_t *x)
     }
 
     // check if number is zero
-    for (d = t; d < t + xlen; ++d) {
+    for (d = t; d < tend; d++) {
       if (*d != 0) break;
-      while (ps<s && s[-1]=='0') s--;
-      goto done;
     }
+    if (d == tend) goto done;
   }
 
  done:
+while (ps<s && s[-1]=='0') s--;
   mrb_free(mrb, t);
   if (x->sn < 0) {
     *s++ = '-';