diff --git a/lib/mpi/mpi-pow.c b/lib/mpi/mpi-pow.c
index a5c921e..2fd7a46 100644
--- a/lib/mpi/mpi-pow.c
+++ b/lib/mpi/mpi-pow.c
@@ -1,22 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /* mpi-pow.c  -  MPI functions
  *	Copyright (C) 1994, 1996, 1998, 2000 Free Software Foundation, Inc.
  *
  * This file is part of GnuPG.
  *
- * GnuPG is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * GnuPG is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
- *
  * Note: This code is heavily based on the GNU MP Library.
  *	 Actually it's the same code with only minor changes in the
  *	 way the data is stored; this is to support the abstraction
@@ -37,6 +24,7 @@
 int mpi_powm(MPI res, MPI base, MPI exp, MPI mod)
 {
 	mpi_ptr_t mp_marker = NULL, bp_marker = NULL, ep_marker = NULL;
+	struct karatsuba_ctx karactx = {};
 	mpi_ptr_t xp_marker = NULL;
 	mpi_ptr_t tspace = NULL;
 	mpi_ptr_t rp, ep, mp, bp;
@@ -163,13 +151,11 @@
 		int c;
 		mpi_limb_t e;
 		mpi_limb_t carry_limb;
-		struct karatsuba_ctx karactx;
 
 		xp = xp_marker = mpi_alloc_limb_space(2 * (msize + 1));
 		if (!xp)
 			goto enomem;
 
-		memset(&karactx, 0, sizeof karactx);
 		negative_result = (ep[0] & 1) && base->sign;
 
 		i = esize - 1;
@@ -294,8 +280,6 @@
 		if (mod_shift_cnt)
 			mpihelp_rshift(rp, rp, rsize, mod_shift_cnt);
 		MPN_NORMALIZE(rp, rsize);
-
-		mpihelp_release_karatsuba_ctx(&karactx);
 	}
 
 	if (negative_result && rsize) {
@@ -312,6 +296,7 @@
 leave:
 	rc = 0;
 enomem:
+	mpihelp_release_karatsuba_ctx(&karactx);
 	if (assign_rp)
 		mpi_assign_limb_space(res, rp, size);
 	if (mp_marker)