diff --git a/.travis.yml b/.travis.yml
index a5dd317..4eb04d6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -21,15 +21,6 @@ env:
 
 addons:
   apt:
-    packages:
-      - g++-4.7
-      - g++-4.8
-      - g++-4.9
-      - g++-5
-      - g++-6
-      - clang-3.6
-      - clang-3.7
-      - clang-3.8
     sources:
       - ubuntu-toolchain-r-test
       - llvm-toolchain-precise
@@ -48,69 +39,156 @@ matrix:
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-4.7 CXXSTD=c++03
+      addons:
+        apt:
+          packages:
+            - g++-4.7
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-4.7 CXXSTD=c++11
+      addons:
+        apt:
+          packages:
+            - g++-4.7
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-4.8 CXXSTD=c++03
+      addons:
+        apt:
+          packages:
+            - g++-4.8
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-4.8 CXXSTD=c++11
+      addons:
+        apt:
+          packages:
+            - g++-4.8
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-4.9 CXXSTD=c++03
+      addons:
+        apt:
+          packages:
+            - g++-4.9
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-4.9 CXXSTD=c++11
+      addons:
+        apt:
+          packages:
+            - g++-4.9
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-5 CXXSTD=c++03
+      addons:
+        apt:
+          packages:
+            - g++-5
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-5 CXXSTD=c++11
+      addons:
+        apt:
+          packages:
+            - g++-5
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-5 CXXSTD=c++14
+      addons:
+        apt:
+          packages:
+            - g++-5
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-6 CXXSTD=c++03
+      addons:
+        apt:
+          packages:
+            - g++-6
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-6 CXXSTD=c++11
+      addons:
+        apt:
+          packages:
+            - g++-6
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-6 CXXSTD=c++14
+      addons:
+        apt:
+          packages:
+            - g++-6
 
     - os: linux
       env: TOOLSET=gcc COMPILER=g++-6 CXXSTD=c++1z
+      addons:
+        apt:
+          packages:
+            - g++-6
 
     - os: linux
       env: TOOLSET=clang COMPILER=clang++ CXXSTD=c++03
 
+    - os: linux
+      env: TOOLSET=clang COMPILER=clang++ CXXSTD=c++11
+
     - os: linux
       env: TOOLSET=clang COMPILER=clang++-3.6 CXXSTD=c++03
+      addons:
+        apt:
+          packages:
+            - clang-3.6
 
     - os: linux
       env: TOOLSET=clang COMPILER=clang++-3.6 CXXSTD=c++11
+      addons:
+        apt:
+          packages:
+            - clang-3.6
 
     - os: linux
       env: TOOLSET=clang COMPILER=clang++-3.7 CXXSTD=c++03
+      addons:
+        apt:
+          packages:
+            - clang-3.7
 
     - os: linux
       env: TOOLSET=clang COMPILER=clang++-3.7 CXXSTD=c++11
+      addons:
+        apt:
+          packages:
+            - clang-3.7
 
     - os: linux
       env: TOOLSET=clang COMPILER=clang++-3.8 CXXSTD=c++03
+      addons:
+        apt:
+          packages:
+            - clang-3.8
 
     - os: linux
       env: TOOLSET=clang COMPILER=clang++-3.8 CXXSTD=c++11
+      addons:
+        apt:
+          packages:
+            - clang-3.8
 
     - os: linux
       env: TOOLSET=clang COMPILER=clang++-3.8 CXXSTD=c++14
+      addons:
+        apt:
+          packages:
+            - clang-3.8
 
     - os: linux
       env: TOOLSET=clang COMPILER=clang++-3.8 CXXSTD=c++1z
+      addons:
+        apt:
+          packages:
+            - clang-3.8
 
     - os: osx
       env: TOOLSET=clang COMPILER=clang++ CXXSTD=c++03