diff --git a/composer.json b/composer.json
index bb478f57..2e609b63 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,7 @@
         }
     ],
     "require": {
-        "php": "^5.3.3 || ^7.0",
+        "php": "^5.3.3 || ^7.0 || ^8.0",
         "symfony/polyfill-ctype": "^1.8"
     },
     "require-dev": {
diff --git a/src/Assert.php b/src/Assert.php
index dd1ffe6e..b28e1784 100644
--- a/src/Assert.php
+++ b/src/Assert.php
@@ -1620,7 +1620,7 @@ public static function propertyNotExists($classOrObject, $property, $message = '
      */
     public static function methodExists($classOrObject, $method, $message = '')
     {
-        if (!\method_exists($classOrObject, $method)) {
+        if (!(\is_string($classOrObject) || \is_object($classOrObject)) || !\method_exists($classOrObject, $method)) {
             static::reportInvalidArgument(\sprintf(
                 $message ?: 'Expected the method %s to exist.',
                 static::valueToString($method)
@@ -1640,7 +1640,7 @@ public static function methodExists($classOrObject, $method, $message = '')
      */
     public static function methodNotExists($classOrObject, $method, $message = '')
     {
-        if (\method_exists($classOrObject, $method)) {
+        if ((\is_string($classOrObject) || \is_object($classOrObject)) && \method_exists($classOrObject, $method)) {
             static::reportInvalidArgument(\sprintf(
                 $message ?: 'Expected the method %s to not exist.',
                 static::valueToString($method)