diff --git a/.github/workflows/tests-levels-matrix.php b/.github/workflows/tests-levels-matrix.php
new file mode 100644
index 0000000000..ecdb0cb964
--- /dev/null
+++ b/.github/workflows/tests-levels-matrix.php
@@ -0,0 +1,32 @@
+<?php declare(strict_types = 1);
+
+shell_exec('php vendor/bin/phpunit --list-tests-xml test-list.xml');
+
+$simpleXml = simplexml_load_file('test-list.xml');
+if ($simpleXml === false) {
+	throw new RuntimeException('Error loading test-list.xml');
+}
+
+$testFilters = [];
+foreach($simpleXml->testCaseClass as $testCaseClass) {
+	foreach($testCaseClass->testCaseMethod as $testCaseMethod) {
+		if ((string) $testCaseMethod['groups'] !== 'levels') {
+			continue;
+		}
+
+		$testCaseName = (string) $testCaseMethod['id'];
+
+		[$className, $testName] = explode('::', $testCaseName, 2);
+		$fileName = 'tests/'. str_replace('\\', DIRECTORY_SEPARATOR, $className) . '.php';
+
+		$filter = str_replace('\\', '\\\\', $testCaseName);
+
+		$testFilters[] = sprintf("%s --filter %s", escapeshellarg($fileName), escapeshellarg($filter));
+	}
+}
+
+if ($testFilters === []) {
+	throw new RuntimeException('No tests found');
+}
+
+echo json_encode($testFilters);
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 805771f017..dc59d0f243 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -98,11 +98,45 @@ jobs:
       - name: "Tests"
         run: "make tests-integration"
 
+  tests-levels-matrix:
+    name: "Determine levels tests matrix"
+    runs-on: ubuntu-latest
+    timeout-minutes: 60
+
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@v3
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          coverage: "none"
+          php-version: "8.3"
+          tools: pecl
+          extensions: ds,mbstring
+          ini-file: development
+          ini-values: memory_limit=1G
+
+      - name: "Install PHPUnit 10.x"
+        run: "composer remove --dev brianium/paratest && composer require --dev --with-all-dependencies phpunit/phpunit:^10"
+
+      - id: set-matrix
+        run: echo "matrix=$(php .github/workflows/tests-levels-matrix.php)" >> $GITHUB_OUTPUT
+
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+
   tests-levels:
+    needs: tests-levels-matrix
+
     name: "Levels tests"
     runs-on: ubuntu-latest
     timeout-minutes: 60
 
+    strategy:
+      matrix:
+        test-filter: "${{fromJson(needs.tests-levels-matrix.outputs.matrix)}}"
+
     steps:
       - name: "Checkout"
         uses: actions/checkout@v3
@@ -121,7 +155,7 @@ jobs:
         run: "composer install --no-interaction --no-progress"
 
       - name: "Tests"
-        run: "make tests-levels"
+        run: "php vendor/bin/phpunit ${{ matrix.test-filter }} --group levels"
 
   tests-old-phpunit:
     name: "Tests with old PHPUnit"
diff --git a/src/Reflection/BetterReflection/SourceLocator/ComposerJsonAndInstalledJsonSourceLocatorMaker.php b/src/Reflection/BetterReflection/SourceLocator/ComposerJsonAndInstalledJsonSourceLocatorMaker.php
index ff9068d835..3d123ccfe2 100644
--- a/src/Reflection/BetterReflection/SourceLocator/ComposerJsonAndInstalledJsonSourceLocatorMaker.php
+++ b/src/Reflection/BetterReflection/SourceLocator/ComposerJsonAndInstalledJsonSourceLocatorMaker.php
@@ -112,6 +112,7 @@ public function create(string $projectInstallationPath): ?SourceLocator
 		foreach ($classMapPaths as $classMapPath) {
 			if (is_dir($classMapPath)) {
 				$locators[] = $this->optimizedDirectorySourceLocatorRepository->getOrCreate($classMapPath);
+				continue;
 			}
 			if (!is_file($classMapPath)) {
 				continue;