diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ba43588..8d3ed01 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -47,4 +47,4 @@ jobs:
       - uses: php-actions/phpstan@v3
         with:
           path: src/
-          level: 7
+          level: 9
diff --git a/src/VersionInfo.php b/src/VersionInfo.php
index 908be71..773b74f 100644
--- a/src/VersionInfo.php
+++ b/src/VersionInfo.php
@@ -320,6 +320,10 @@ public function getNextVersion(
             $branch = $this->branch;
         }
 
+        if ($release === null) {
+            throw new Exception('Could not determine the release.', __LINE__);
+        }
+
         return new self(
             integerversion: (int) $integerversion,
             decimalversion: $decimalversion,