diff --git a/ChangeLog b/ChangeLog
index 41cfe335782d7f7bc84178fcd1357ccb660be6d7..7be5b10dd682d75de4e3f1e8123a56c61a9eebf0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2019-04-30  Niels Möller  <nisse@lysator.liu.se>
+
+	Based on a patch contributed by Nikos Mavrogiannopoulos.
+	* cmac.c (_cmac128_block_mulx): Renamed function...
+	(block_mulx): ... from old name.
+	* cmac-internal.h (_cmac128_block_mulx): New file, declare function.
+	* Makefile.in (DISTFILES): Added cmac-internal.h.
+
 2019-04-27  Niels Möller  <nisse@lysator.liu.se>
 
 	From Simo Sorce:
diff --git a/Makefile.in b/Makefile.in
index 440de9f7bb59211d3fea3da59296ad677cd106eb..fefc7887cce4b9fff2e71bfbebe205ce71b50d53 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -229,7 +229,7 @@ DISTFILES = $(SOURCES) $(HEADERS) getopt.h getopt_int.h \
 	INSTALL NEWS ChangeLog \
 	nettle.pc.in hogweed.pc.in \
 	$(des_headers) descore.README desdata.stamp \
-	aes-internal.h camellia-internal.h serpent-internal.h \
+	aes-internal.h camellia-internal.h cmac-internal.h serpent-internal.h \
 	cast128_sboxes.h desinfo.h desCode.h \
 	ripemd160-internal.h sha2-internal.h \
 	memxor-internal.h nettle-internal.h nettle-write.h \
diff --git a/cmac-internal.h b/cmac-internal.h
new file mode 100644
index 0000000000000000000000000000000000000000..80db7fcc58cd494474fb0c0a43c5b8110813d00a
--- /dev/null
+++ b/cmac-internal.h
@@ -0,0 +1,54 @@
+/* cmac-internal.h
+
+   CMAC mode internal functions
+
+   Copyright (C) 2017 Red Hat, Inc.
+
+   Contributed by Nikos Mavrogiannopoulos
+
+   This file is part of GNU Nettle.
+
+   GNU Nettle is free software: you can redistribute it and/or
+   modify it under the terms of either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * 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.
+
+   or both in parallel, as here.
+
+   GNU Nettle 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 copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see http://www.gnu.org/licenses/.
+*/
+
+#ifndef NETTLE_CMAC_INTERNAL_H_INCLUDED
+#define NETTLE_CMAC_INTERNAL_H_INCLUDED
+
+#include "cmac.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define _cmac128_block_mulx _nettle_cmac128_block_mulx
+
+void _cmac128_block_mulx(union nettle_block16 *out,
+			 const union nettle_block16 *in);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* CMAC_INTERNAL_H_INCLUDED */
diff --git a/cmac.c b/cmac.c
index ed3b5eb8f613c7115f11ffada7f88c3608c79cf4..2f15a74d81e6c0d3a402821a6596324dc1868c5b 100644
--- a/cmac.c
+++ b/cmac.c
@@ -44,13 +44,14 @@
 
 #include "memxor.h"
 #include "nettle-internal.h"
+#include "cmac-internal.h"
 #include "macros.h"
 
 /* shift one and XOR with 0x87. */
 #if WORDS_BIGENDIAN
-static void
-block_mulx(union nettle_block16 *dst,
-	   const union nettle_block16 *src)
+void
+_cmac128_block_mulx(union nettle_block16 *dst,
+		    const union nettle_block16 *src)
 {
   uint64_t carry = src->u64[0] >> 63;
   dst->u64[0] = (src->u64[0] << 1) | (src->u64[1] >> 63);
@@ -59,9 +60,9 @@ block_mulx(union nettle_block16 *dst,
 #else /* !WORDS_BIGENDIAN */
 #define LE_SHIFT(x) ((((x) & 0x7f7f7f7f7f7f7f7f) << 1) | \
                      (((x) & 0x8080808080808080) >> 15))
-static void
-block_mulx(union nettle_block16 *dst,
-	   const union nettle_block16 *src)
+void
+_cmac128_block_mulx(union nettle_block16 *dst,
+		    const union nettle_block16 *src)
 {
   uint64_t carry = (src->u64[0] & 0x80) >> 7;
   dst->u64[0] = LE_SHIFT(src->u64[0]) | ((src->u64[1] & 0x80) << 49);
@@ -83,8 +84,8 @@ cmac128_set_key(struct cmac128_ctx *ctx, const void *cipher,
   /* step 1 - generate subkeys k1 and k2 */
   encrypt(cipher, 16, L->b, const_zero);
 
-  block_mulx(&ctx->K1, L);
-  block_mulx(&ctx->K2, &ctx->K1);
+  _cmac128_block_mulx(&ctx->K1, L);
+  _cmac128_block_mulx(&ctx->K2, &ctx->K1);
 }
 
 #define MIN(x,y) ((x)<(y)?(x):(y))