diff --git a/.travis-before_install.sh b/.travis-before_install.sh
index 20884bd7..b587f6da 100755
--- a/.travis-before_install.sh
+++ b/.travis-before_install.sh
@@ -40,7 +40,7 @@ if [ "$Compiler_version" != "" ] && [ "$Compiler_version" != "default" ]; then
     if [ "$Compiler_name" = "gcc" ]; then
 	sudo apt-get install -qq gcc-${Compiler_version} g++-${Compiler_version}
     elif [ "$Compiler_name" = "clang" ]; then
-	sudo apt-get install -qq clang-${Compiler_version}
+	sudo apt-get --allow-unauthenticated install -qq --force-yes clang-${Compiler_version}
     fi
 fi
 
diff --git a/.travis.yml b/.travis.yml
index 781e9c90..621aed48 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,6 +8,7 @@ matrix:
     - os: linux
       compiler: gcc
       env: Tr_Compiler_Version="6"
+      dist: trusty
       # https://launchpad.net/~ubuntu-toolchain-r/+archive/ubuntu/test
     - os: linux
       compiler: gcc
@@ -26,7 +27,7 @@ matrix:
       #compiler: clang
       #env: Tr_Compiler_Version="default" # broken compiler
     - os: osx
-      osx_image: xcode8
+      osx_image: xcode7.3
       env: Tr_Xcode_Version="8"
       # https://docs.travis-ci.com/user/osx-ci-environment/#OS-X-Version
     - os: osx