diff --git a/app/Dav/AddressBookBackend.php b/app/Dav/AddressBookBackend.php
index 39370629..5207e5ba 100644
--- a/app/Dav/AddressBookBackend.php
+++ b/app/Dav/AddressBookBackend.php
@@ -155,8 +155,9 @@ class AddressBookBackend extends AbstractBackend
      * If the backend supports this, it may allow for some speed-ups.
      *
      * @param mixed $addressBookId
+     * @param array<int, string> $uris
      *
-     * @return array
+     * @return array<int, mixed>
      */
     public function getMultipleCards($addressBookId, array $uris)
     {
diff --git a/app/Dav/Principal.php b/app/Dav/Principal.php
index 5700ac0a..a5c32d54 100644
--- a/app/Dav/Principal.php
+++ b/app/Dav/Principal.php
@@ -136,10 +136,11 @@ class Principal implements PrincipalBackendInterface
      *
      * @param string $principal
      *
-     * @return array
+     * @return array<int, string>|null
      */
     public function getGroupMemberSet($principal)
     {
+        return [];
     }
 
     /**
@@ -147,7 +148,7 @@ class Principal implements PrincipalBackendInterface
      *
      * @param string $principal
      *
-     * @return array
+     * @return array<int, string>|null
      */
     public function getGroupMembership($principal)
     {
@@ -155,7 +156,7 @@ class Principal implements PrincipalBackendInterface
             return null;
         }
 
-        return ['addressbooks/'.$matches[1]];
+        return ['addressbooks/' . $matches[1]];
     }
 
     /**
@@ -164,6 +165,8 @@ class Principal implements PrincipalBackendInterface
      * The principals should be passed as a list of uri's.
      *
      * @param string $principal
+     * @param array<int, string> $members
+     * @return void
      */
     public function setGroupMemberSet($principal, array $members)
     {
@@ -176,7 +179,7 @@ class Principal implements PrincipalBackendInterface
     {
         return [
             '{DAV:}displayname' => $user->name,
-            'uri' => 'principals/'.$user->email,
+            'uri' => 'principals/' . $user->email,
             '{http://sabredav.org/ns}email-address' => $user->email,
         ];
     }
diff --git a/app/Dav/ServiceProvider.php b/app/Dav/ServiceProvider.php
index b32ca6af..f5ffd0be 100644
--- a/app/Dav/ServiceProvider.php
+++ b/app/Dav/ServiceProvider.php
@@ -9,6 +9,7 @@ use Sabre\CardDAV\AddressBookRoot;
 use Sabre\CardDAV\Plugin as CardDAVPlugin;
 use Sabre\DAV\Auth\Plugin as AuthPlugin;
 use Sabre\DAV\Browser\Plugin as BrowserPlugin;
+use Sabre\DAV\ServerPlugin;
 use Sabre\DAVACL\AbstractPrincipalCollection;
 use Sabre\DAVACL\Plugin as AclPlugin;
 use Sabre\DAVACL\PrincipalCollection;
@@ -50,6 +51,9 @@ class ServiceProvider extends BaseServiceProvider
         ];
     }
 
+    /**
+     * @return array<int, ServerPlugin>
+     */
     private function plugins(): array
     {
         $authBackend = new AuthBackend();
diff --git a/app/Exceptions/Handler.php b/app/Exceptions/Handler.php
index d9aa7d89..1a8fd144 100644
--- a/app/Exceptions/Handler.php
+++ b/app/Exceptions/Handler.php
@@ -12,15 +12,14 @@ class Handler extends ExceptionHandler
     /**
      * A list of the exception types that are not reported.
      *
-     * @var string[]
+     * @var array<int, class-string<Throwable>>
      */
-    protected $dontReport = [
-    ];
+    protected $dontReport = [];
 
     /**
      * A list of the inputs that are never flashed for validation exceptions.
      *
-     * @var string[]
+     * @var array<int, string>
      */
     protected $dontFlash = [
         'password',
diff --git a/phpstan.neon b/phpstan.neon
index 62723251..fbb941ef 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -34,61 +34,6 @@ parameters:
             count: 1
             path: app/Activity.php
 
-        -
-            message: "#^Method App\\\\Dav\\\\AddressBookBackend\\:\\:getMultipleCards\\(\\) has parameter \\$uris with no value type specified in iterable type array\\.$#"
-            count: 1
-            path: app/Dav/AddressBookBackend.php
-
-        -
-            message: "#^Method App\\\\Dav\\\\AddressBookBackend\\:\\:getMultipleCards\\(\\) return type has no value type specified in iterable type array\\.$#"
-            count: 1
-            path: app/Dav/AddressBookBackend.php
-
-        -
-            message: "#^Method App\\\\Dav\\\\Principal\\:\\:getGroupMemberSet\\(\\) return type has no value type specified in iterable type array\\.$#"
-            count: 1
-            path: app/Dav/Principal.php
-
-        -
-            message: "#^Method App\\\\Dav\\\\Principal\\:\\:getGroupMemberSet\\(\\) should return array but return statement is missing\\.$#"
-            count: 1
-            path: app/Dav/Principal.php
-
-        -
-            message: "#^Method App\\\\Dav\\\\Principal\\:\\:getGroupMembership\\(\\) return type has no value type specified in iterable type array\\.$#"
-            count: 1
-            path: app/Dav/Principal.php
-
-        -
-            message: "#^Method App\\\\Dav\\\\Principal\\:\\:getGroupMembership\\(\\) should return array but returns null\\.$#"
-            count: 1
-            path: app/Dav/Principal.php
-
-        -
-            message: "#^Method App\\\\Dav\\\\Principal\\:\\:setGroupMemberSet\\(\\) has no return type specified\\.$#"
-            count: 1
-            path: app/Dav/Principal.php
-
-        -
-            message: "#^Method App\\\\Dav\\\\Principal\\:\\:setGroupMemberSet\\(\\) has parameter \\$members with no value type specified in iterable type array\\.$#"
-            count: 1
-            path: app/Dav/Principal.php
-
-        -
-            message: "#^Method App\\\\Dav\\\\ServiceProvider\\:\\:plugins\\(\\) return type has no value type specified in iterable type array\\.$#"
-            count: 1
-            path: app/Dav/ServiceProvider.php
-
-        -
-            message: "#^PHPDoc type array\\<string\\> of property App\\\\Exceptions\\\\Handler\\:\\:\\$dontFlash is not covariant with PHPDoc type array\\<int, string\\> of overridden property Illuminate\\\\Foundation\\\\Exceptions\\\\Handler\\:\\:\\$dontFlash\\.$#"
-            count: 1
-            path: app/Exceptions/Handler.php
-
-        -
-            message: "#^PHPDoc type array\\<string\\> of property App\\\\Exceptions\\\\Handler\\:\\:\\$dontReport is not covariant with PHPDoc type array\\<int, class\\-string\\<Throwable\\>\\> of overridden property Illuminate\\\\Foundation\\\\Exceptions\\\\Handler\\:\\:\\$dontReport\\.$#"
-            count: 1
-            path: app/Exceptions/Handler.php
-
         -
             message: "#^Method App\\\\Http\\\\Controllers\\\\Auth\\\\RegisterController\\:\\:create\\(\\) has parameter \\$data with no value type specified in iterable type array\\.$#"
             count: 1