diff --git a/.travis.yml b/.travis.yml
index c4a2149..335fd9f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -42,7 +42,7 @@
         # (Updating the version is fine as long as no warnings are raised by doing so.)
         - python -m pip install sphinx~=1.6.1
       script:
-        - make check suspicious html SPHINXOPTS="-q -W"
+        - make check suspicious html SPHINXOPTS="-q -W -j4"
     - os: linux
       language: c
       compiler: gcc