diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 7b987aa..f088ba2 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -32,14 +32,14 @@ variables:
   # See the documentation here:                                                 #
   # https://wayland.freedesktop.org/libinput/doc/latest/building_libinput.html  #
   ###############################################################################
-  FEDORA_PACKAGES: 'git diffutils gcc gcc-c++ pkgconf-pkg-config meson systemd-devel libxkbcommon-devel doxygen python3-attrs python3-pytest python3-dbusmock python3-jinja2 '
+  FEDORA_PACKAGES: 'git diffutils gcc gcc-c++ pkgconf-pkg-config meson systemd-devel libxkbcommon-devel libxml2 doxygen python3-attrs python3-pytest python3-dbusmock python3-jinja2 '
   ############################ end of package lists #############################
 
   # these tags should be updated each time the list of packages is updated
   # changing these will force rebuilding the associated image
   # Note: these tags have no meaning and are not tied to a particular
   # libinput version
-  FEDORA_TAG:  '2023-02-02.0'
+  FEDORA_TAG:  '2023-02-23.0'
 
   FDO_UPSTREAM_REPO: libinput/libei
 
diff --git a/.gitlab-ci/config.yml b/.gitlab-ci/config.yml
index 555fb2f..573fafa 100644
--- a/.gitlab-ci/config.yml
+++ b/.gitlab-ci/config.yml
@@ -3,7 +3,7 @@
 #
 
 # We're happy to rebuild all containers when one changes.
-.default_tag: &default_tag '2023-02-02.0'
+.default_tag: &default_tag '2023-02-23.0'
 
 distributions:
   - name: fedora
@@ -20,6 +20,7 @@ distributions:
       - meson
       - systemd-devel
       - libxkbcommon-devel
+      - libxml2
       - doxygen
       - python3-attrs
       - python3-pytest
diff --git a/proto/meson.build b/proto/meson.build
index 20759ac..6f6cbf7 100644
--- a/proto/meson.build
+++ b/proto/meson.build
@@ -1,2 +1,10 @@
 scanner = find_program('ei-scanner')
 protocol_xml = files('protocol.xml')
+protocol_dtd = files('protocol.dtd')
+
+xmllint = find_program('xmllint', required: false)
+if xmllint.found()
+    test('dtdcheck', xmllint,
+         args: ['--dtdvalid', protocol_dtd, protocol_xml]
+         )
+endif
diff --git a/proto/protocol.dtd b/proto/protocol.dtd
new file mode 100644
index 0000000..ee062ee
--- /dev/null
+++ b/proto/protocol.dtd
@@ -0,0 +1,32 @@
+<!ELEMENT protocol (copyright?, description?, interface+)>
+  <!ATTLIST protocol name CDATA #REQUIRED>
+<!ELEMENT copyright (#PCDATA)>
+<!ELEMENT interface (description?,(request|event|enum)+)>
+  <!ATTLIST interface name CDATA #REQUIRED>
+  <!ATTLIST interface version CDATA #REQUIRED>
+<!ELEMENT request (description?,arg*)>
+  <!ATTLIST request name CDATA #REQUIRED>
+  <!ATTLIST request type CDATA #IMPLIED>
+  <!ATTLIST request since CDATA #IMPLIED>
+<!ELEMENT event (description?,arg*)>
+  <!ATTLIST event name CDATA #REQUIRED>
+  <!ATTLIST event type CDATA #IMPLIED>
+  <!ATTLIST event since CDATA #IMPLIED>
+<!ELEMENT enum (description?,entry*)>
+  <!ATTLIST enum name CDATA #REQUIRED>
+  <!ATTLIST enum since CDATA #IMPLIED>
+  <!ATTLIST enum bitfield CDATA #IMPLIED>
+<!ELEMENT entry (description?)>
+  <!ATTLIST entry name CDATA #REQUIRED>
+  <!ATTLIST entry value CDATA #REQUIRED>
+  <!ATTLIST entry summary CDATA #IMPLIED>
+  <!ATTLIST entry since CDATA #IMPLIED>
+<!ELEMENT arg (description?)>
+  <!ATTLIST arg name CDATA #REQUIRED>
+  <!ATTLIST arg type CDATA #REQUIRED>
+  <!ATTLIST arg summary CDATA #IMPLIED>
+  <!ATTLIST arg interface CDATA #IMPLIED>
+  <!ATTLIST arg allow-null CDATA #IMPLIED>
+  <!ATTLIST arg enum CDATA #IMPLIED>
+<!ELEMENT description (#PCDATA)>
+  <!ATTLIST description summary CDATA #REQUIRED>