diff --git a/expat/CMakeLists.txt b/expat/CMakeLists.txt
index 4a5ea2b5..0537be3e 100644
--- a/expat/CMakeLists.txt
+++ b/expat/CMakeLists.txt
@@ -393,6 +393,7 @@ set(_EXPAT_C_SOURCES
     lib/xmlrole.c
     lib/xmltok.c
 # NOTE: ISO C forbids an empty translation unit
+#   lib/xcsinc.c
 #   lib/xmltok_impl.c
 #   lib/xmltok_ns.c
 )
diff --git a/expat/lib/Makefile.am b/expat/lib/Makefile.am
index 1958f322..e6f62b18 100644
--- a/expat/lib/Makefile.am
+++ b/expat/lib/Makefile.am
@@ -80,6 +80,7 @@ EXTRA_DIST = \
     siphash.h \
     utf8tab.h \
     winconfig.h \
+    xcsinc.c \
     xmlrole.h \
     xmltok.h \
     xmltok_impl.c \
diff --git a/expat/lib/xcsinc.c b/expat/lib/xcsinc.c
new file mode 100644
index 00000000..3597c248
--- /dev/null
+++ b/expat/lib/xcsinc.c
@@ -0,0 +1,48 @@
+/* This file is included from other .c files!
+                            __  __            _
+                         ___\ \/ /_ __   __ _| |_
+                        / _ \\  /| '_ \ / _` | __|
+                       |  __//  \| |_) | (_| | |_
+                        \___/_/\_\ .__/ \__,_|\__|
+                                 |_| XML parser
+
+   Copyright (c) 2022 Sebastian Pipping <sebastian@pipping.org>
+   Licensed under the MIT license:
+
+   Permission is  hereby granted,  free of charge,  to any  person obtaining
+   a  copy  of  this  software   and  associated  documentation  files  (the
+   "Software"),  to  deal in  the  Software  without restriction,  including
+   without  limitation the  rights  to use,  copy,  modify, merge,  publish,
+   distribute, sublicense, and/or sell copies of the Software, and to permit
+   persons  to whom  the Software  is  furnished to  do so,  subject to  the
+   following conditions:
+
+   The above copyright  notice and this permission notice  shall be included
+   in all copies or substantial portions of the Software.
+
+   THE  SOFTWARE  IS  PROVIDED  "AS  IS",  WITHOUT  WARRANTY  OF  ANY  KIND,
+   EXPRESS  OR IMPLIED,  INCLUDING  BUT  NOT LIMITED  TO  THE WARRANTIES  OF
+   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+   NO EVENT SHALL THE AUTHORS OR  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+   DAMAGES OR  OTHER LIABILITY, WHETHER  IN AN  ACTION OF CONTRACT,  TORT OR
+   OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+   USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+static size_t
+xcslen(const XML_Char *s) {
+#ifdef XML_UNICODE
+#  ifdef XML_UNICODE_WCHAR_T
+  return wcslen(s);
+#  else
+  // XML_Char is unsigned short
+  size_t len = 0;
+  while (s[len]) {
+    len++;
+  }
+  return len;
+#  endif
+#else
+  return strlen(s);
+#endif
+}