diff --git a/tox.ini b/tox.ini
index 890d15e9..a9bbeda1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,6 +13,7 @@ deps =
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/test-requirements.txt
 commands = python setup.py test --slowest --testr-args="{posargs}"
+whitelist_externals = bash
 
 [testenv:integration]
 setenv =
@@ -30,6 +31,8 @@ downloadcache = ~/cache/pip
 commands =
     flake8 {posargs}
     {toxinidir}/tools/config/check_uptodate.sh
+    # Check that .po and .pot files are valid:
+    bash -c "find sahara -type f -regex '.*\.pot?' -print0|xargs -0 -n 1 msgfmt --check-format -o /dev/null"
 
 [testenv:venv]
 commands = {posargs}