diff --git a/composer.json b/composer.json
index 2fdac32..7bc9f04 100644
--- a/composer.json
+++ b/composer.json
@@ -21,14 +21,14 @@
         }
     },
     "require": {
-        "php": "^7.1",
+        "php": "^5.6|^7.1|^7.2",
         "friendsofphp/php-cs-fixer": "^2.1",
-        "phpunit/phpunit": "~6.0|~7.0|~8",
+        "phpunit/phpunit": "^3.7|~6.0|~7.0|~8",
         "squizlabs/php_codesniffer": "~3.0",
-        "phpmd/phpmd": "~2.6",
-        "symfony/dependency-injection": "~4.0",
-        "symfony/config": "~4.0",
-        "symfony/yaml": "~4.0",
+        "phpmd/phpmd": "*",
+        "symfony/dependency-injection": "~3.0|~4.0",
+        "symfony/config": "*",
+        "symfony/yaml": "*",
         "fiunchinho/phpunit-randomizer": "~3.0|~4.0",
         "seld/jsonlint": "~1.5",
         "bruli/ignore-files": "~1.0",