diff --git a/tools/testing/selftests/ftrace/ftracetest b/tools/testing/selftests/ftrace/ftracetest
index 0a56bf209f6c..a610097794ae 100755
--- a/tools/testing/selftests/ftrace/ftracetest
+++ b/tools/testing/selftests/ftrace/ftracetest
@@ -7,6 +7,9 @@
 #  Written by Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
 #
 
+# Keep command output parsing stable regardless of the user's locale.
+export LC_ALL=C
+
 usage() { # errno [message]
 [ ! -z "$2" ] && echo $2
 echo "Usage: ftracetest [options] [testcase(s)] [testcase-directory(s)]"