diff --git a/pep8.travis.sh b/pep8.travis.sh
index ccac0a435..13a727596 100755
--- a/pep8.travis.sh
+++ b/pep8.travis.sh
@@ -1,7 +1,12 @@
 #!/bin/sh
+
+set -e  # Fail fast
+
+# PEP8 is not ignored in ACME
+pep8 acme
+
 pep8 \
   setup.py \
-  acme \
   letsencrypt \
   letsencrypt-apache \
   letsencrypt-nginx \