diff --git a/tests/git-scripts/pre-commit.sh b/tests/git-scripts/pre-commit.sh
new file mode 100755
index 0000000..4365686
--- /dev/null
+++ b/tests/git-scripts/pre-commit.sh
@@ -0,0 +1,36 @@
+#!/bin/sh
+
+# pre-commit.sh
+#
+# Copyright (c) 2017, ARM Limited, All Rights Reserved
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# This file is part of Mbed TLS (https://tls.mbed.org)
+
+# Purpose
+#
+# This script does quick sanity checks before commiting:
+#   - check that generated files are up-to-date.
+#
+# It is meant to be called as a git pre-commit hook, see README.md.
+#
+# From the git sample pre-commit hook:
+#   Called by "git commit" with no arguments.  The hook should
+#   exit with non-zero status after issuing an appropriate message if
+#   it wants to stop the commit.
+
+set -eu
+
+tests/scripts/check-generated-files.sh
diff --git a/tests/scripts/check-generated-files.sh b/tests/scripts/check-generated-files.sh
index 516437e..5776daa 100755
--- a/tests/scripts/check-generated-files.sh
+++ b/tests/scripts/check-generated-files.sh
@@ -50,11 +50,29 @@
 
 set -eu
 
+if [ $# -ne 0 ] && [ "$1" = "--help" ]; then
+    cat <<EOF
+$0 [-u]
+This script checks that all generated file are up-to-date. If some aren't, by
+default the scripts reports it and exits in error; with the -u option, it just
+updates them instead.
+
+  -u    Update the files rather than return an error for out-of-date files.
+EOF
+    exit
+fi
+
 if [ -d library -a -d include -a -d tests ]; then :; else
     echo "Must be run from mbed TLS root" >&2
     exit 1
 fi
 
+UPDATE=
+if [ $# -ne 0 ] && [ "$1" = "-u" ]; then
+    shift
+    UPDATE='y'
+fi
+
 check()
 {
     SCRIPT=$1
@@ -80,9 +98,15 @@
     for FILE in $FILES; do
         if ! diff $FILE $FILE.bak >/dev/null 2>&1; then
             echo "'$FILE' was either modified or deleted by '$SCRIPT'"
-            exit 1
+            if [ -z "$UPDATE" ]; then
+                exit 1
+            fi
         fi
-        mv $FILE.bak $FILE
+        if [ -z "$UPDATE" ]; then
+            mv $FILE.bak $FILE
+        else
+            rm $FILE.bak
+        fi
 
         if [ -d $TO_CHECK ]; then
             # Create a grep regular expression that we can check against the
@@ -99,7 +123,9 @@
         # Check if there are any new files
         if ls -1 $TO_CHECK | grep -v "$PATTERN" >/dev/null 2>&1; then
             echo "Files were created by '$SCRIPT'"
-            exit 1
+            if [ -z "$UPDATE" ]; then
+                exit 1
+            fi
         fi
     fi
 }