diff --git a/ChangeLog b/ChangeLog
index 292dab4..751e7d2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 2017-07-19  NIIBE Yutaka  <gniibe@fsij.org>
 
+	* src/mod.c (mod_inv): Clear TMP.
+
 	* src/configure (REVISION): Generate even when no git.
 
 	* polarssl/library/bignum.c (mpi_exp_mod): Call mpi_grow for X
diff --git a/src/mod.c b/src/mod.c
index bd4de24..340fc16 100644
--- a/src/mod.c
+++ b/src/mod.c
@@ -156,6 +156,7 @@ mod_inv (bn256 *C, const bn256 *X, const bn256 *N)
 #define borrow carry
   int n = MAX_GCD_STEPS_BN256;
 
+  memset (tmp, 0, sizeof (bn256));
   memset (C, 0, sizeof (bn256));
   memcpy (u, X, sizeof (bn256));
   memcpy (v, N, sizeof (bn256));