diff --git a/.travis.sh b/.travis.sh
index 522d82353..434187e4f 100755
--- a/.travis.sh
+++ b/.travis.sh
@@ -22,19 +22,8 @@ function build_and_test ()
     sudo update-alternatives --set gcc /usr/bin/gcc-$GCC_VERSION
   fi
 
-  # gcc is too slow and we have a time limit in Travis CI: selective builds.
-  if [ "$BUILD_EXAMPLES" == "1" ]; then
-    GTSAM_BUILD_EXAMPLES_ALWAYS=ON
-  else
-    GTSAM_BUILD_EXAMPLES_ALWAYS=OFF
-  fi
-  if [ "$RUN_TESTS" == "1" ]; then
-    GTSAM_BUILD_TESTS=ON
-  else
-    GTSAM_BUILD_TESTS=OFF
-  fi
-
   cmake $SOURCE_DIR \
+      -DGTSAM_BUILD_UNSTABLE=$GTSAM_BUILD_UNSTABLE \
       -DGTSAM_BUILD_EXAMPLES_ALWAYS=$GTSAM_BUILD_EXAMPLES_ALWAYS \
       -DGTSAM_BUILD_TESTS=$GTSAM_BUILD_TESTS
 
@@ -42,10 +31,13 @@ function build_and_test ()
   make -j2
 
   # Run tests:
-  if [ "$RUN_TESTS" == "1" ]; then
+  if [ "$GTSAM_BUILD_TESTS" == "ON" ]; then
     make check
   fi
 
+  # Print ccache stats
+  ccache -s
+
   cd $SOURCE_DIR
 }
 
diff --git a/.travis.yml b/.travis.yml
index bce676721..4b4487103 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -16,8 +16,12 @@ addons:
     - libpython-dev python-numpy
     - libboost-all-dev
 
-before_install:
-  - if [ "$TRAVIS_OS_NAME" == "osx" ]; then brew update          ; fi
+# before_install:
+#  - if [ "$TRAVIS_OS_NAME" == "osx" ]; then brew update          ; fi
+
+install:
+  - if [ "$TRAVIS_OS_NAME" == "osx" ]; then HOMEBREW_NO_AUTO_UPDATE=1 brew install ccache  ; fi
+  - if [ "$TRAVIS_OS_NAME" == "osx" ]; then export PATH="/usr/local/opt/ccache/libexec:$PATH" ; fi
 
 script:
   - bash .travis.sh
@@ -27,23 +31,24 @@ env:
     - MAKEFLAGS="-j 2"
     - CCACHE_SLOPPINESS=pch_defines,time_macros
 
+# gcc is too slow and we have a time limit in Travis CI: selective builds.
 matrix:
   include:
   - compiler: gcc
     os: linux
-    env: BUILD_EXAMPLES=1
+    env: GTSAM_BUILD_UNSTABLE=ON GTSAM_BUILD_EXAMPLES_ALWAYS=ON GTSAM_BUILD_TESTS=OFF
   - compiler: gcc
     os: linux
-    env: RUN_TESTS=1
+    env: GTSAM_BUILD_UNSTABLE=OFF GTSAM_BUILD_EXAMPLES_ALWAYS=OFF GTSAM_BUILD_TESTS=ON # gcc too slow for all tests
   - compiler: gcc
     os: linux
-    env: BUILD_EXAMPLES=1 GCC_VERSION="8"
+    env: GTSAM_BUILD_UNSTABLE=ON GTSAM_BUILD_EXAMPLES_ALWAYS=ON GTSAM_BUILD_TESTS=OFF GCC_VERSION="8"
   - compiler: clang
     os: linux
-    env: BUILD_EXAMPLES=1
-  - compiler: gcc
-    os: osx
-    env: BUILD_EXAMPLES=1
+    env: GTSAM_BUILD_UNSTABLE=ON GTSAM_BUILD_EXAMPLES_ALWAYS=ON GTSAM_BUILD_TESTS=OFF
+# - compiler: gcc
+#   os: osx
+#   env: GTSAM_BUILD_UNSTABLE=ON GTSAM_BUILD_EXAMPLES_ALWAYS=ON GTSAM_BUILD_TESTS=OFF
   - compiler: clang
     os: osx
-    env: RUN_TESTS=1
+    env: GTSAM_BUILD_UNSTABLE=ON GTSAM_BUILD_EXAMPLES_ALWAYS=OFF GTSAM_BUILD_TESTS=ON