diff --git a/lib/SimpleSAML/Auth/Simple.php b/lib/SimpleSAML/Auth/Simple.php
index ac9e5afe8a1ba01b9273e16b3725460230bdd1ba..2be23efc9705c580e84ac0b4caf46d88e48db32c 100644
--- a/lib/SimpleSAML/Auth/Simple.php
+++ b/lib/SimpleSAML/Auth/Simple.php
@@ -391,6 +391,7 @@ class Simple
             $port = '';
         }
 
+        /** @psalm-var \SimpleSAML\Configuration $this->app_config */
         $base = trim($this->app_config->getString(
             'baseURL',
             $scheme . '://' . $host . $port
diff --git a/lib/SimpleSAML/Error/Exception.php b/lib/SimpleSAML/Error/Exception.php
index 5177fd64d70514328a6cfede9bc9eaf4dcb30e38..9af638d9efa94c34aef98d89cda3a3f2fc12327e 100644
--- a/lib/SimpleSAML/Error/Exception.php
+++ b/lib/SimpleSAML/Error/Exception.php
@@ -33,7 +33,7 @@ class Exception extends \Exception
     /**
      * The cause of this exception.
      *
-     * @var Exception|null
+     * @var \SimpleSAML\Error\Exception|null
      */
     private $cause = null;
 
@@ -68,7 +68,7 @@ class Exception extends \Exception
      *
      * @param \Throwable $e The exception.
      *
-     * @return Exception The new exception.
+     * @return \SimpleSAML\Error\Exception The new exception.
      */
     public static function fromException(Throwable $e): Exception
     {
diff --git a/lib/SimpleSAML/Error/UnserializableException.php b/lib/SimpleSAML/Error/UnserializableException.php
index 287475590a77aac54307544e2e95dcb1a4b78a9a..5c7d21206e884900c903362fe20a5a4ed35eaff5 100644
--- a/lib/SimpleSAML/Error/UnserializableException.php
+++ b/lib/SimpleSAML/Error/UnserializableException.php
@@ -42,8 +42,8 @@ class UnserializableException extends Exception
         $msg = $original->getMessage();
         $code = $original->getCode();
 
-        if (is_string($code)) {
-            // PDOException uses a string as the code. Filter it out here.
+        if (!is_int($code)) {
+            // PDOException and possibly others use a string for the code. Filter it out here.
             $code = -1;
         }
 
diff --git a/lib/SimpleSAML/Locale/Translate.php b/lib/SimpleSAML/Locale/Translate.php
index abec8afeaa26bdedc14ae3a098b75265d48e784c..5db3acc1ee5bdfe07eb8210de91e232910290b25 100644
--- a/lib/SimpleSAML/Locale/Translate.php
+++ b/lib/SimpleSAML/Locale/Translate.php
@@ -526,6 +526,7 @@ class Translate
 
         // we don't have a translation for the current language, load alternative priorities
         $sspcfg = Configuration::getInstance();
+        /** @psalm-var \SimpleSAML\Configuration $langcfg */
         $langcfg = $sspcfg->getConfigItem('language');
         $priorities = $langcfg->getArray('priorities', []);
 
diff --git a/lib/SimpleSAML/Metadata/SAMLBuilder.php b/lib/SimpleSAML/Metadata/SAMLBuilder.php
index 04a1b5d335983eefac8e0b767bf66061173b7f01..60adb3003c5aa1c600a9d2f90ccb5e195650d113 100644
--- a/lib/SimpleSAML/Metadata/SAMLBuilder.php
+++ b/lib/SimpleSAML/Metadata/SAMLBuilder.php
@@ -155,6 +155,8 @@ class SAMLBuilder
 
         $metadata = Configuration::loadFromArray($metadata, $metadata['entityid']);
         $defaultEndpoint = $metadata->getDefaultEndpoint('SingleSignOnService');
+
+        /** @psalm-suppress UndefinedClass */
         $e = new SecurityTokenServiceType();
         $e->setLocation($defaultEndpoint['Location']);
 
diff --git a/lib/SimpleSAML/Metadata/Sources/MDQ.php b/lib/SimpleSAML/Metadata/Sources/MDQ.php
index e98bcf212f646e96185338aae4dce1eeb6658f82..833ae7608eafb3bd20fec06c09d21d888de46549 100644
--- a/lib/SimpleSAML/Metadata/Sources/MDQ.php
+++ b/lib/SimpleSAML/Metadata/Sources/MDQ.php
@@ -247,9 +247,7 @@ class MDQ extends \SimpleSAML\Metadata\MetaDataStorageSource
             case 'shib13-sp-remote':
                 return $entity->getMetadata1xSP();
             case 'attributeauthority-remote':
-                $ret = $entity->getAttributeAuthorities();
-                return $ret[0];
-
+                return $entity->getAttributeAuthorities();
             default:
                 Logger::warning(__CLASS__ . ': unknown metadata set: \'' . $set . '\'.');
         }
diff --git a/lib/SimpleSAML/Module.php b/lib/SimpleSAML/Module.php
index 861452149012ef84b8efe015a04ea4dc233e55b6..c68cf5e36cac105c19acd788dcc1e228aecaacaa 100644
--- a/lib/SimpleSAML/Module.php
+++ b/lib/SimpleSAML/Module.php
@@ -187,7 +187,7 @@ class Module
             $request->request->all(),
             $request->attributes->all(),
             $request->cookies->all(),
-            $request_files ?? [],
+            $request_files,
             $request->server->all(),
             $request->getContent()
         );
@@ -291,14 +291,16 @@ class Module
             }
         }
 
+        /** @psalm-var \SimpleSAML\Configuration $assetConfig */
         $assetConfig = $config->getConfigItem('assets');
+        /** @psalm-var \SimpleSAML\Configuration $cacheConfig */
         $cacheConfig = $assetConfig->getConfigItem('caching');
         $response = new BinaryFileResponse($path);
         $response->setCache([
             // "public" allows response caching even if the request was authenticated,
             // which is exactly what we want for static resources
             'public' => true,
-            'max_age' => (string)$cacheConfig->getInteger('max_age', 86400)
+            'max_age' => strval($cacheConfig->getInteger('max_age', 86400))
         ]);
         $response->setAutoLastModified();
         if ($cacheConfig->getBoolean('etag', false)) {