diff --git a/.travis.yml b/.travis.yml
index 9a3456a9..e635925a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,7 +2,9 @@ language: ruby
 rvm:
   - "2.5.0"
 sudo: false
-cache: bundler
+cache:
+  - bundler
+  - $TRAVIS_BUILD_DIR/doxygen-src/build/bin
 env:
   # http://docs.travis-ci.com/user/environment-variables/#Global-Variables
   global:
diff --git a/scripts/build-install-doxygen.sh b/scripts/build-install-doxygen.sh
index 9624971d..fc5f1a78 100644
--- a/scripts/build-install-doxygen.sh
+++ b/scripts/build-install-doxygen.sh
@@ -1,6 +1,8 @@
 #!/bin/sh
 set -ex
 
+echo $(ls doxygen-src/build/bin)
+
 # Build instructions from: https://www.stack.nl/~dimitri/doxygen/download.html
 echo "Cloning doxygen repository..."
 git clone https://github.com/doxygen/doxygen.git doxygen-src