diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index c7432a5..600c390 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -21,6 +21,7 @@ jobs:
           - "8.2"
           - "8.3"
           - "8.4"
+          - "8.5"
         dependencies:
           - lowest
           - highest
@@ -72,6 +73,11 @@ jobs:
         if: ${{ matrix.dependencies == 'highest' && matrix.platform-reqs == 'ignore-platform-reqs' }}
         run: composer update --no-interaction --ignore-platform-reqs
 
+      # PHP 8.4 deprecates implicit nullable parameters, and psalm depends on many packages needing a higher version that fixes this.
+      - name: Install highest dependencies for psalm
+        working-directory: vendor-bin/psalm
+        run: composer update --no-interaction
+
       - name: Run tests
         run: composer test
 
diff --git a/composer.json b/composer.json
index 0066bc8..a8d368d 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,7 @@
     }
   ],
   "require": {
-    "php": "~8.1.0 || ~8.2.0 || ~8.3.0 || ~8.4.0",
+    "php": "~8.1.0 || ~8.2.0 || ~8.3.0 || ~8.4.0 || ~8.5.0",
     "ext-json": "*",
     "ext-intl": "*"
   },
diff --git a/docker-compose.yml b/docker-compose.yml
index 506fd06..c124689 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -28,4 +28,11 @@ services:
       dockerfile: php-8.4.Dockerfile
     volumes:
       - .:/app
-    working_dir: /app
\ No newline at end of file
+    working_dir: /app
+  php8.5:
+    build:
+      context: .
+      dockerfile: php-8.5.Dockerfile
+    volumes:
+      - .:/app
+    working_dir: /app
diff --git a/php-8.5.Dockerfile b/php-8.5.Dockerfile
new file mode 100644
index 0000000..a206617
--- /dev/null
+++ b/php-8.5.Dockerfile
@@ -0,0 +1,27 @@
+FROM php:8.5-cli
+
+RUN apt-get update &&  apt-get install -y \
+      zip \
+      git \
+      wget \
+      gpg \
+      libicu-dev && \
+    pecl install xdebug && \
+    docker-php-ext-enable xdebug && \
+    docker-php-ext-configure intl --enable-intl && \
+    docker-php-ext-install intl pcntl && \
+    echo "xdebug.mode = develop,coverage,debug" >> "$PHP_INI_DIR/conf.d/docker-php-ext-xdebug.ini"
+
+ENV COMPOSER_ALLOW_SUPERUSER=1 \
+    COMPOSER_PROCESS_TIMEOUT=1200
+
+RUN curl --silent --show-error https://getcomposer.org/installer | php -- \
+      --install-dir=/usr/bin --filename=composer && \
+    git config --global --add safe.directory "*"
+
+RUN wget -O phive.phar https://phar.io/releases/phive.phar && \
+    wget -O phive.phar.asc https://phar.io/releases/phive.phar.asc && \
+    gpg --keyserver hkps://keys.openpgp.org --recv-keys 0x9D8A98B29B2D5D79 && \
+    gpg --verify phive.phar.asc phive.phar && \
+    chmod +x phive.phar && \
+    mv phive.phar /usr/local/bin/phive \
diff --git a/src/Comparator/EqualValueComparator.php b/src/Comparator/EqualValueComparator.php
index 19795cd..7aa498a 100644
--- a/src/Comparator/EqualValueComparator.php
+++ b/src/Comparator/EqualValueComparator.php
@@ -111,10 +111,10 @@ private function getPropertiesWithoutDuplicates(Iterator $valueIterator): array|
         $valuesByProperty = [];
         while ($valueIterator->valid()) {
             $property = $valueIterator->key();
-            if (isset($valuesByProperty[$property])) {
+            if ($property === null) {
                 return null;
             }
-            if ($property === null) {
+            if (isset($valuesByProperty[$property])) {
                 return null;
             }
             $valuesByProperty[$property] = $valueIterator->current();
diff --git a/vendor-bin/cs/composer.json b/vendor-bin/cs/composer.json
index 31bfe6e..d963d69 100644
--- a/vendor-bin/cs/composer.json
+++ b/vendor-bin/cs/composer.json
@@ -1,5 +1,5 @@
 {
     "require-dev": {
-        "squizlabs/php_codesniffer": "^3.8"
+        "squizlabs/php_codesniffer": "^4.0.1"
     }
 }
diff --git a/vendor-bin/psalm/composer.json b/vendor-bin/psalm/composer.json
index 7c112e0..22ae594 100644
--- a/vendor-bin/psalm/composer.json
+++ b/vendor-bin/psalm/composer.json
@@ -1,6 +1,6 @@
 {
     "require-dev": {
-        "vimeo/psalm": "^6.5.1",
+        "vimeo/psalm": "^6.16.1",
         "psalm/plugin-phpunit": "^0.19.5"
     },
     "conflict": {