diff --git a/circle.yml b/circle.yml
index f40298150..e577070a1 100644
--- a/circle.yml
+++ b/circle.yml
@@ -14,12 +14,33 @@ dependencies:
     - sudo cp ./scripts/influxdb_conf.toml /etc/opt/influxdb/influxdb.conf
     - sudo /opt/influxdb/influxd -config /etc/opt/influxdb/influxdb.conf: {background: true}
     - sudo cp scripts/nginx_proxy.conf /etc/nginx/conf.d/proxy.conf
-    - sudo service nginx restart
+    - sudo service nginx stop
+    - sleep 2
+    - sudo service nginx start
     - sed -i 's/^;//' ~/.phpenv/versions/$(phpenv global)/etc/conf.d/xdebug.ini
+  override:
+    - phpenv global 5.6.5
+    - composer install --prefer-source --no-interaction
+    - phpenv global 5.5.21
+    - composer install --prefer-source --no-interaction
 
 test:
   override:
+    - phpenv global 5.6.5
     - vendor/bin/phpunit --coverage-clover clover.xml
+    - composer require guzzlehttp/guzzle:~6 --prefer-source --no-interaction --update-with-dependencies
+    - vendor/bin/phpunit
+    - composer require guzzlehttp/guzzle:~5 --prefer-source --no-interaction --update-with-dependencies
+    - vendor/bin/phpunit
+    - composer require guzzlehttp/guzzle:~4 --prefer-source --no-interaction --update-with-dependencies
+    - vendor/bin/phpunit
+    - phpenv global 5.5.21
+    - composer require guzzlehttp/guzzle:~6 --prefer-source --no-interaction --update-with-dependencies
+    - vendor/bin/phpunit
+    - composer require guzzlehttp/guzzle:~5 --prefer-source --no-interaction --update-with-dependencies
+    - vendor/bin/phpunit
+    - composer require guzzlehttp/guzzle:~4 --prefer-source --no-interaction --update-with-dependencies
+    - vendor/bin/phpunit
   post:
     - wget https://scrutinizer-ci.com/ocular.phar
     - php ocular.phar code-coverage:upload --format=php-clover clover.xml
diff --git a/composer.json b/composer.json
index 6abce12da..8f65257b5 100644
--- a/composer.json
+++ b/composer.json
@@ -4,7 +4,7 @@
     "description": "Send your app metrics to InfluxDB",
     "require": {
          "php": ">=5.4",
-         "guzzlehttp/guzzle": "~4|~5|~6",
+         "guzzlehttp/guzzle": "4.2.*",
          "zendframework/zend-stdlib": "~2",
          "zendframework/zend-filter": "~2",
          "zendframework/zend-servicemanager": "~2"