diff --git a/tests/compat-test b/tests/compat-test
index 25ba8c6e..0884ed4f 100755
--- a/tests/compat-test
+++ b/tests/compat-test
@@ -171,6 +171,8 @@ function valgrind_run()
 	INFOSTRING="$(basename ${BASH_SOURCE[1]})-line-${BASH_LINENO[0]}" ./valg.sh ${CRYPTSETUP_VALGRIND} "$@"
 }
 
+export LANG=C
+
 [ -n "$VALG" ] && valgrind_setup && CRYPTSETUP=valgrind_run
 
 # LUKS non-root-tests
diff --git a/tests/compat-test2 b/tests/compat-test2
index 70f47916..c14a0681 100755
--- a/tests/compat-test2
+++ b/tests/compat-test2
@@ -201,6 +201,8 @@ function load_key()
 	keyctl add $@ >/dev/null
 }
 
+export LANG=C
+
 [ -n "$VALG" ] && valgrind_setup && CRYPTSETUP=valgrind_run
 
 [ $(id -u) != 0 ] && skip "WARNING: You must be root to run this test, test skipped."