diff --git a/.travis.yml b/.travis.yml
index da82445..6af5f34 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,14 +8,6 @@ cache:
     directories:
         - $HOME/.composer/cache/files
 
-php:
-    - 5.4
-    - 5.5
-    - 5.6
-    - 7.0
-    - 7.1
-    - hhvm
-
 env:
     global:
         - TEST_COMMAND="composer test"
@@ -27,18 +19,47 @@ branches:
 matrix:
     fast_finish: true
     include:
+        - php: 7.1
+          env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest" DEPENDENCIES="doctrine/instantiator:^1.1"
+
+          # Test the latest stable release
         - php: 5.4
-          env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest" COVERAGE=true TEST_COMMAND="composer test-ci"
+        - php: 5.5
+        - php: 5.6
+        - php: 7.0
+        - php: 7.1
+        - php: 7.2
+          env: COVERAGE=true TEST_COMMAND="composer test-ci"  DEPENDENCIES="henrikbjorn/phpspec-code-coverage:^1.0"
+
+          # Test LTS versions
+        - php: 7.1
+          env: DEPENDENCIES="dunglas/symfony-lock:^2"
+        - php: 7.1
+          env: DEPENDENCIES="dunglas/symfony-lock:^3"
+        - php: 7.1
+          env: DEPENDENCIES="dunglas/symfony-lock:^4" STABILITY="rc"
+
+          # Latest dev release
+        - php: 7.1
+          env: STABILITY="dev"
 
+    allow_failures:
+          # Latest dev is allowed to fail.
+        - env: STABILITY="dev"
+          
 before_install:
     - if [[ $COVERAGE != true ]]; then phpenv config-rm xdebug.ini || true; fi
+    - if ! [ -z "$STABILITY" ]; then composer config minimum-stability ${STABILITY}; fi;
+    - if ! [ -z "$DEPENDENCIES" ]; then composer require --no-update ${DEPENDENCIES}; fi;
 
 install:
+    - cat composer.json
     # To be removed when this issue will be resolved: https://github.com/composer/composer/issues/5355
-    - if [[ "$COMPOSER_FLAGS" == *"--prefer-lowest"* ]]; then travis_retry composer update --prefer-dist --no-interaction --prefer-stable --quiet; fi
-    - travis_retry composer update ${COMPOSER_FLAGS} --prefer-dist --no-interaction
+    - if [[ "$COMPOSER_FLAGS" == *"--prefer-lowest"* ]]; then composer update --prefer-dist --no-interaction --prefer-stable --quiet; fi
+    - composer update ${COMPOSER_FLAGS} --prefer-dist --no-interaction
 
 script:
+    - composer validate --strict --no-check-lock
     - $TEST_COMMAND
 
 after_success:
diff --git a/composer.json b/composer.json
index c2c9ec4..fc5fc5f 100644
--- a/composer.json
+++ b/composer.json
@@ -11,15 +11,14 @@
         }
     ],
     "require": {
-        "php": ">=5.4",
+        "php": "^5.4 || ^7.0",
         "php-http/httplug": "^1.1",
         "php-http/message-factory": "^1.0",
         "php-http/message": "^1.6",
         "symfony/options-resolver": "^2.6 || ^3.0 || ^4.0"
     },
     "require-dev": {
-        "phpspec/phpspec": "^2.4",
-        "henrikbjorn/phpspec-code-coverage" : "^1.0",
+        "phpspec/phpspec": "^2.5 || ^3.4 || ^4.2",
         "guzzlehttp/psr7": "^1.4"
     },
     "suggest": {
diff --git a/src/Plugin/ContentTypePlugin.php b/src/Plugin/ContentTypePlugin.php
index 2390ca6..8ef1d62 100644
--- a/src/Plugin/ContentTypePlugin.php
+++ b/src/Plugin/ContentTypePlugin.php
@@ -102,7 +102,7 @@ private function isJson($stream)
 
         json_decode($stream->getContents());
 
-        return JSON_ERROR_NONE == json_last_error();
+        return JSON_ERROR_NONE === json_last_error();
     }
 
     /**