diff --git a/.travis.sh b/.travis.sh
index bb8ebc8c..acbe37ac 100755
--- a/.travis.sh
+++ b/.travis.sh
@@ -58,6 +58,9 @@ elif [[ ${MODE} = cmake-oos ]]; then
     find ROOT -printf "%P\n" | sort
 elif [[ ${MODE} = cppcheck ]]; then
     cppcheck --quiet --error-exitcode=1 .
+elif [[ ${MODE} = clang-format ]]; then
+    ./apply-clang-format.sh
+    git diff --exit-code
 else
     ./qa.sh ${CONFIGURE_ARGS}
 fi
diff --git a/.travis.yml b/.travis.yml
index 01dd26e7..71a434a3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -21,6 +21,8 @@ env:
 
 matrix:
   include:
+    - os: linux
+      env: MODE=clang-format
     - os: linux
       env: MODE=cmake-oos CMAKE_ARGS=-DXML_ATTR_INFO=ON
     - os: linux
@@ -46,6 +48,7 @@ addons:
       - ubuntu-toolchain-r-test
     packages:
       - clang-9
+      - clang-format-9
       - cmake
       - cppcheck
       - docbook2x
diff --git a/expat/apply-clang-format.sh b/expat/apply-clang-format.sh
new file mode 100755
index 00000000..420b62c4
--- /dev/null
+++ b/expat/apply-clang-format.sh
@@ -0,0 +1,49 @@
+#! /usr/bin/env bash
+#                          __  __            _
+#                       ___\ \/ /_ __   __ _| |_
+#                      / _ \\  /| '_ \ / _` | __|
+#                     |  __//  \| |_) | (_| | |_
+#                      \___/_/\_\ .__/ \__,_|\__|
+#                               |_| XML parser
+#
+# Copyright (c) 2019 Expat development team
+# 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.
+
+set -e
+set -u
+set -o pipefail
+
+find \
+        -name '*.[ch]' \
+        -o -name '*.cpp' \
+        -o -name '*.cxx' \
+        -o -name '*.h.cmake' \
+    | sort \
+    | xargs clang-format -i -style=file -verbose
+
+dos2unix expat_config.h.cmake
+sed \
+        -e 's, @$,@,' \
+        -e 's,#\( \+\)cmakedefine,\1#cmakedefine,' \
+        -i \
+        expat_config.h.cmake
+unix2dos expat_config.h.cmake