diff --git a/mrbgems/mruby-bigint/core/bigint.c b/mrbgems/mruby-bigint/core/bigint.c
index 33229c72d..13a7901bf 100644
--- a/mrbgems/mruby-bigint/core/bigint.c
+++ b/mrbgems/mruby-bigint/core/bigint.c
@@ -200,7 +200,6 @@ uadd(mrb_state *mrb, mpz_t *z, mpz_t *x, mpz_t *y)
     c >>= DIG_SIZE;
   }
   z->p[y->sz] = (mp_limb)c;
-  trim(z);
 }
 
 /* z = y - x, ignoring sign */