diff --git a/.travis.yml b/.travis.yml
index ca8fea8..bfc13d1 100755
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,11 +1,6 @@
 language: php
 
 php:
-  - 5.4
-  - 5.5
-  - 5.6
-  - 7.0
-  - 7.1
   - 7.2
   - 7.3
 
diff --git a/README.md b/README.md
index 995f139..cbb48b3 100644
--- a/README.md
+++ b/README.md
@@ -38,8 +38,6 @@ class Action extends Enum
 }
 ```
 
-Note the `private` keyword requires PHP 7.1 or higher, you can omit it on PHP 7.0.
-
 ## Usage
 
 ```php
diff --git a/composer.json b/composer.json
index 88bbe16..3a10886 100644
--- a/composer.json
+++ b/composer.json
@@ -22,7 +22,7 @@
         }
     },
     "require": {
-        "php": ">=5.4",
+        "php": ">=7.2",
         "ext-json": "*"
     },
     "require-dev": {
diff --git a/src/Enum.php b/src/Enum.php
index 58b69b3..2999d31 100644
--- a/src/Enum.php
+++ b/src/Enum.php
@@ -87,7 +87,7 @@ public function __toString()
      *
      * @return bool
      */
-    final public function equals($variable = null)
+    final public function equals($variable = null): bool
     {
         return $variable instanceof self
             && $this->getValue() === $variable->getValue()