diff --git a/.travis.yml b/.travis.yml
index aa281529..f457db81 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,31 +2,53 @@ language: cpp
 
 sudo: false
 
-compiler:
-  - gcc
+matrix:
+  include:
+    - os: linux
+      compiler: gcc
+      addons:
+        apt:
+          sources: ['ubuntu-toolchain-r-test']
+          packages: ['g++-4.8', 'valgrind']
+      env: COMPILER=g++-4.8
 
-env:
-  - COMPILER=g++-4.9
-  - COMPILER=g++-5
-  - COMPILER=clang-3.6
+    - os: linux
+      compiler: gcc
+      addons:
+        apt:
+          sources: ['ubuntu-toolchain-r-test']
+          packages: ['g++-4.9', 'valgrind', 'python-pip', 'python-yaml']
+      before_script:
+        - pip install --user git+git://github.com/eddyxu/cpp-coveralls.git
+      env: COMPILER=g++-4.9
 
-addons:
-  apt:
-    sources:
-    - ubuntu-toolchain-r-test
-    - llvm-toolchain-precise
-    - llvm-toolchain-precise-3.6
-    - llvm-toolchain-precise-3.7
-    packages:
-    - g++-4.9
-    - g++-5
-    - clang-3.6
-    - valgrind
-    - python-pip
-    - python-yaml
+    - os: linux
+      compiler: gcc
+      addons:
+        apt:
+          sources: ['ubuntu-toolchain-r-test']
+          packages: ['g++-5', 'valgrind']
+      env: COMPILER=g++-5
 
-before_script:
-  - pip install --user git+git://github.com/eddyxu/cpp-coveralls.git
+    - os: linux
+      compiler: clang
+      env: COMPILER=clang++
+
+    - os: linux
+      compiler: clang
+      addons:
+        apt:
+          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.5']
+          packages: ['clang-3.5', 'valgrind']
+      env: COMPILER=clang++-3.5
+
+    - os: linux
+      compiler: clang
+      addons:
+        apt:
+          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.6']
+          packages: ['clang-3.6', 'valgrind']
+      env: COMPILER=clang++-3.6
 
 script:
   - make CXX=$COMPILER CXXFLAGS="-lstdc++"
diff --git a/Makefile b/Makefile
index 950cae5e..71a1175f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,3 +1,5 @@
+.PHONY: pretty clean
+
 # used programs
 RE2C = re2c
 SED = sed