diff --git a/mrbgems/mruby-bigint/core/bigint.c b/mrbgems/mruby-bigint/core/bigint.c
index f18a80ed4..f481f17ac 100644
--- a/mrbgems/mruby-bigint/core/bigint.c
+++ b/mrbgems/mruby-bigint/core/bigint.c
@@ -1764,6 +1764,7 @@ mrb_bint_powm(mrb_state *mrb, mrb_value x, mrb_value exp, mrb_value mod)
     }
     mpz_powm_i(mrb, &z, &a, e, &c);
   }
+  mpz_clear(mrb, &c);
   return bint_norm(mrb, bint_new(mrb, &z));
 }