diff --git a/expat/CMakeLists.txt b/expat/CMakeLists.txt
index b2ae0451..fc2c68d6 100644
--- a/expat/CMakeLists.txt
+++ b/expat/CMakeLists.txt
@@ -3,6 +3,34 @@
 
 cmake_minimum_required(VERSION 3.1.3)
 
+# This allows controlling documented build time switches
+# when Expat is pulled in using the add_subdirectory function, e.g.
+#
+#   set(EXPAT_BUILD_DOCS OFF)
+#   set(EXPAT_BUILD_TOOLS OFF)
+#   add_subdirectory(${expat_SOURCE_DIR}/expat ${expat_BINARY_DIR})
+#
+# would disable compilation of the xmlwf CLI and its man page.
+# Without activating behaviour NEW for policy CMP0077 here,
+# a user with -Wdev enabled would see warning
+#
+#   Policy CMP0077 is not set: option() honors normal variables.  Run "cmake
+#   --help-policy CMP0077" for policy details.  Use the cmake_policy command to
+#   set the policy and suppress this warning.
+#
+#   For compatibility with older versions of CMake, option is clearing the
+#   normal variable 'EXPAT_BUILD_DOCS'.
+#
+# and effectively not be able to adjust option EXPAT_BUILD_DOCS.
+#
+# For more details please see:
+# - https://cmake.org/cmake/help/latest/policy/CMP0077.html
+# - https://github.com/libexpat/libexpat/pull/419
+#
+if(POLICY CMP0077)
+    cmake_policy(SET CMP0077 NEW)
+endif()
+
 project(expat
     VERSION
         2.2.9
diff --git a/expat/Changes b/expat/Changes
index a7ca17cf..9d696888 100644
--- a/expat/Changes
+++ b/expat/Changes
@@ -27,7 +27,7 @@ Release x.x.x xxx xxxxxxxxx xx xxxx
                     involving -DEXPAT_CHAR_TYPE=(ushort|wchar_t)
             #360  CMake: Install pre-compiled shipped xmlwf.1 manpage in case
                     of -DEXPAT_BUILD_DOCS=OFF
-       #375 #380  CMake: Fix use of Expat by means of add_subdirectory
+  #375 #380 #419  CMake: Fix use of Expat by means of add_subdirectory
        #407 #408  CMake: Keep expat target name constant at "expat"
                     (i.e. refrain from using the target name to control
                     build artifact filenames)
@@ -42,6 +42,7 @@ Release x.x.x xxx xxxxxxxxx xx xxxx
         Special thanks to:
             asavah
             Ben Wagner
+            Frank Landgraf
             Jeffrey Walton
             Joe Orton
             Kleber Tarcísio