diff --git a/ChangeLog b/ChangeLog
index 8d00b72..11d4c39 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2020-09-07  NIIBE Yutaka  <gniibe@fsij.org>
+
+	* src/modp256r1.c (modp256r1_add, modp256r1_sub)
+	(modp256r1_reduce): Use memmove.
+
+	*  (modp256k1_add, modp256k1_sub): Use memmove.
+
 2020-09-04  NIIBE Yutaka  <gniibe@fsij.org>
 
 	* src/openpgp-do.c (GPG_DO_ALG_INFO): New.
diff --git a/src/modp256k1.c b/src/modp256k1.c
index c296453..94c7154 100644
--- a/src/modp256k1.c
+++ b/src/modp256k1.c
@@ -1,7 +1,7 @@
 /*
  * modp256k1.c -- modulo arithmetic for p256k1
  *
- * Copyright (C) 2014, 2016 Free Software Initiative of Japan
+ * Copyright (C) 2014, 2016, 2020 Free Software Initiative of Japan
  * Author: NIIBE Yutaka <gniibe@fsij.org>
  *
  * This file is a part of Gnuk, a GnuPG USB Token implementation.
@@ -76,7 +76,7 @@ modp256k1_add (bn256 *X, const bn256 *A, const bn256 *B)
   cond &= bn256_sub (tmp, X, P256K1);
   if (cond)
     /* No-carry AND borrow */
-    memcpy (tmp, tmp, sizeof (bn256));
+    memmove (tmp, tmp, sizeof (bn256));
   else
     memcpy (X, tmp, sizeof (bn256));
 }
@@ -95,7 +95,7 @@ modp256k1_sub (bn256 *X, const bn256 *A, const bn256 *B)
   if (borrow)
     memcpy (X, tmp, sizeof (bn256));
   else
-    memcpy (tmp, tmp, sizeof (bn256));
+    memmove (tmp, tmp, sizeof (bn256));
 }
 
 /**
diff --git a/src/modp256r1.c b/src/modp256r1.c
index 90518c5..d22a480 100644
--- a/src/modp256r1.c
+++ b/src/modp256r1.c
@@ -1,7 +1,7 @@
 /*
  * modp256r1.c -- modulo arithmetic for p256r1
  *
- * Copyright (C) 2011, 2013, 2014, 2016
+ * Copyright (C) 2011, 2013, 2014, 2016, 2020
  *               Free Software Initiative of Japan
  * Author: NIIBE Yutaka <gniibe@fsij.org>
  *
@@ -71,7 +71,7 @@ modp256r1_add (bn256 *X, const bn256 *A, const bn256 *B)
   cond &= bn256_sub (tmp, X, P256R1);
   if (cond)
     /* No-carry AND borrow */
-    memcpy (tmp, tmp, sizeof (bn256));
+    memmove (tmp, tmp, sizeof (bn256));
   else
     memcpy (X, tmp, sizeof (bn256));
 }
@@ -90,7 +90,7 @@ modp256r1_sub (bn256 *X, const bn256 *A, const bn256 *B)
   if (borrow)
     memcpy (X, tmp, sizeof (bn256));
   else
-    memcpy (tmp, tmp, sizeof (bn256));
+    memmove (tmp, tmp, sizeof (bn256));
 }
 
 /**
@@ -122,7 +122,7 @@ modp256r1_reduce (bn256 *X, const bn512 *A)
   S1->word[0] = A->word[0];
   borrow = bn256_sub (tmp0, S1, P256R1);
   if (borrow)
-    memcpy (tmp0, tmp0, sizeof (bn256));
+    memmove (tmp0, tmp0, sizeof (bn256));
   else
     memcpy (S1, tmp0, sizeof (bn256));
   /* X = S1 */
@@ -166,7 +166,7 @@ modp256r1_reduce (bn256 *X, const bn512 *A)
   S5->word[0] = A->word[9];
   borrow = bn256_sub (tmp0, S5, P256R1);
   if (borrow)
-    memcpy (tmp0, tmp0, sizeof (bn256));
+    memmove (tmp0, tmp0, sizeof (bn256));
   else
     memcpy (S5, tmp0, sizeof (bn256));
   /* X += S5 */
@@ -180,7 +180,7 @@ modp256r1_reduce (bn256 *X, const bn512 *A)
   S6->word[0] = A->word[11];
   borrow = bn256_sub (tmp0, S6, P256R1);
   if (borrow)
-    memcpy (tmp0, tmp0, sizeof (bn256));
+    memmove (tmp0, tmp0, sizeof (bn256));
   else
     memcpy (S6, tmp0, sizeof (bn256));
   /* X -= S6 */
@@ -195,7 +195,7 @@ modp256r1_reduce (bn256 *X, const bn512 *A)
   S7->word[0] = A->word[12];
   borrow = bn256_sub (tmp0, S7, P256R1);
   if (borrow)
-    memcpy (tmp0, tmp0, sizeof (bn256));
+    memmove (tmp0, tmp0, sizeof (bn256));
   else
     memcpy (S7, tmp0, sizeof (bn256));
   /* X -= S7 */