diff --git a/.travis.yml b/.travis.yml
index 6c51f5e8..1d865b3e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,6 +10,7 @@ addons:
     - texlive-fonts-recommended
     - texlive-latex-extra
     - latex-xcolor
+    - graphviz
 
 env:
   global:
diff --git a/graph-lib/README.md b/graph-lib/README.md
index 26fdc3aa..1e8aedee 100644
--- a/graph-lib/README.md
+++ b/graph-lib/README.md
@@ -6,8 +6,8 @@ How to build this project
 
 To install the build dependencies of this project on a clean Ubuntu 14.04
 machine, first install a recent [snapshot version of
- racket](https://pre.racket-lang.org/installers/). Then run the following
- commands:
+ racket](https://pre.racket-lang.org/installers/). You will also need
+to install `graphviz`. Then run the following commands:
 
     cd graph-lib/
     sudo apt-get install git