diff --git a/.travis.yml b/.travis.yml
index 1a283e5..379acf6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,27 @@
 sudo: true
 language: crystal
+os:
+  - linux
+#  - osx
+
 install:
   - ./travis-install-lib-sodium.sh
 before_script:
-  - export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib
+  - export C_INCLUDE_PATH=$LD_LIBRARY_PATH:`pwd`/sodium/include
+  - export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`pwd`/sodium/lib
+  - env | egrep PKG
+  - export PKG_CONFIG_PATH=`pwd`/sodium/lib/pkgconfig
+  - env | egrep LD_
+  - env | egrep PKG
+  - pwd
+cache:
+  directories:
+    - sodium
+
+#addons:
+#  apt:
+#    packages:
+#      - libsodium-dev # old
+#  homebrew:
+#    packages:
+#      - libsodium # takes forever
diff --git a/travis-install-lib-sodium.sh b/travis-install-lib-sodium.sh
index 784d02c..146b780 100755
--- a/travis-install-lib-sodium.sh
+++ b/travis-install-lib-sodium.sh
@@ -5,9 +5,21 @@
 
 set -e
 
-wget https://download.libsodium.org/libsodium/releases/LATEST.tar.gz
-tar xvfz LATEST.tar.gz
-cd libsodium-stable
-sudo ./configure
-sudo make
-sudo make install
+LIBSODIUM_INSTALL_PATH=`pwd`/sodium
+
+if [ ! -f "sodium/include/sodium.h" ]; then
+	set -x
+
+	mkdir -p "$LIBSODIUM_INSTALL_PATH"
+	find "$LIBSODIUM_INSTALL_PATH"
+
+	wget https://download.libsodium.org/libsodium/releases/LATEST.tar.gz
+	tar xfz LATEST.tar.gz
+	cd libsodium-stable
+	./configure --prefix="$LIBSODIUM_INSTALL_PATH"
+	make
+	make install
+else
+	echo "using cached libsodium build"
+	find "$LIBSODIUM_INSTALL_PATH"
+fi