diff --git a/include/mes/lib.h b/include/mes/lib.h
index d806d0cc..42f0d568 100644
--- a/include/mes/lib.h
+++ b/include/mes/lib.h
@@ -71,4 +71,6 @@ long __mesabi_idiv (long a, long b);
 unsigned long __mesabi_umod (unsigned long a, unsigned long b);
 unsigned long __mesabi_udiv (unsigned long a, unsigned long b);
 
+void *__memcpy (void *dest, void const *src, size_t n);
+
 #endif //__MES_LIB_H
diff --git a/lib/string/__memcpy.c b/lib/string/__memcpy.c
new file mode 100644
index 00000000..17503071
--- /dev/null
+++ b/lib/string/__memcpy.c
@@ -0,0 +1,31 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2016,2017,2018,2019,2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes 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 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes 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 GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <mes/lib.h>
+
+void *
+__memcpy (void *dest, void const *src, size_t n)
+{
+  char *p = dest;
+  char const *q = src;
+  while (n--)
+    *p++ = *q++;
+  return dest;
+}