diff --git a/.travis.yml b/.travis.yml
index b586fea..0cf082b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,20 +10,22 @@ cache:
 
 jobs:
   fast_finish: true
-  allow_failures:
-    - php: 'nightly'
   include:
     - name: "CI - 8.0"
-      php: 'nightly'
+      php: '8.0'
+      env:
+        - COMPOSER_FLAGS='--ignore-platform-req=php'
     - name: "CI - 7.4"
       php: '7.4'
+      env:
+        - COMPOSER_FLAGS=''
 
 before_install:
   - phpenv config-rm xdebug.ini || return 0
 
 install:
   - composer self-update
-  - composer install --no-interaction --prefer-dist
+  - composer install --no-interaction --prefer-dist $COMPOSER_FLAGS
 
 script:
   - mkdir build
diff --git a/composer.json b/composer.json
index d0ed268..0b44ae9 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
         "laminas/laminas-servicemanager": "^3.4"
     },
     "require-dev": {
-        "infection/infection": "^0.19.2",
+        "infection/infection": "^0.20",
         "phpstan/phpstan": "^0.12.52",
         "phpunit/phpunit": "^9.4",
         "roave/security-advisories": "dev-master",
diff --git a/src/Factory/DottedAccessConfigAbstractFactory.php b/src/Factory/DottedAccessConfigAbstractFactory.php
index bb3016d..23833ff 100644
--- a/src/Factory/DottedAccessConfigAbstractFactory.php
+++ b/src/Factory/DottedAccessConfigAbstractFactory.php
@@ -10,6 +10,7 @@
 use Laminas\ServiceManager\Factory\AbstractFactoryInterface;
 use Shlinkio\Shlink\Config\Exception\InvalidArgumentException;
 
+use function array_key_exists;
 use function array_shift;
 use function explode;
 use function is_array;
@@ -57,7 +58,7 @@ private function readKeysFromArray(array $keys, $array)
         $key = array_shift($keys);
 
         // As soon as one of the provided keys is not found, throw an exception
-        if (! isset($array[$key])) {
+        if (! array_key_exists($key, $array)) {
             throw new InvalidArgumentException(sprintf(
                 'The key "%s" provided in the dotted notation could not be found in the array service',
                 $key,
diff --git a/test/Factory/DottedAccessConfigAbstractFactoryTest.php b/test/Factory/DottedAccessConfigAbstractFactoryTest.php
index 8e8161c..8d6242f 100644
--- a/test/Factory/DottedAccessConfigAbstractFactoryTest.php
+++ b/test/Factory/DottedAccessConfigAbstractFactoryTest.php
@@ -47,20 +47,32 @@ public function throwsExceptionWhenFirstPartOfTheServiceIsNotRegistered(): void
         $this->factory->__invoke(new ServiceManager(), 'foo.bar');
     }
 
-    /** @test */
-    public function dottedNotationIsRecursivelyResolvedUntilLastValueIsFoundAndReturned(): void
-    {
-        $expected = 'this is the result';
-
+    /**
+     * @test
+     * @dataProvider provideDotValues
+     */
+    public function dottedNotationIsRecursivelyResolvedUntilLastValueIsFoundAndReturned(
+        string $serviceName,
+        ?string $expected
+    ): void {
         $result = $this->factory->__invoke(new ServiceManager(['services' => [
             'foo' => [
-                'bar' => ['baz' => $expected],
+                'bar' => [
+                    'baz' => 'this is the result',
+                    'nullable_baz' => null,
+                ],
             ],
-        ]]), 'foo.bar.baz');
+        ]]), $serviceName);
 
         $this->assertEquals($expected, $result);
     }
 
+    public function provideDotValues(): iterable
+    {
+        yield 'non-null value' => ['foo.bar.baz', 'this is the result'];
+        yield 'null value' => ['foo.bar.nullable_baz', null];
+    }
+
     /** @test */
     public function exceptionIsThrownIfAnyStepCannotBeResolved(): void
     {