diff --git a/.github/workflows/phpunit.yml b/.github/workflows/phpunit.yml
index ab400e8f..06a3e103 100644
--- a/.github/workflows/phpunit.yml
+++ b/.github/workflows/phpunit.yml
@@ -13,12 +13,12 @@ jobs:
       # report every PHP version, not only the first failing one
       fail-fast: false
       matrix:
-        php: ['8.2', '8.3', '8.4']
+        php: ['8.2', '8.3', '8.4', '8.5']
         deps: ['locked']
         include:
           # composer.lock is resolved for PHP 8.2; projects on a newer PHP get newer
           # dependencies (e.g. symfony/html-sanitizer 8), so test them as well
-          - php: '8.4'
+          - php: '8.5'
             deps: 'latest'
 
     steps:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2e8abc7a..9c581796 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,21 @@ All notable changes to this project are documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/)
 and the project follows [Semantic Versioning](https://semver.org/).
 
+## [4.8.1] - unreleased
+
+### Fixed
+
+- `UploadField` uses `finfo` as an object to get the mime type of the file. `finfo_close()`
+  is deprecated as of PHP 8.5, so every upload with a type check gave a deprecation notice.
+- `ImageConverter` (`resizeImage()`, `mergeImage()`) frees its images with `unset()`.
+  `imagedestroy()` is deprecated as of PHP 8.5; it has no effect since PHP 8.0, when GD
+  images became objects.
+
+### Changed
+
+- GitHub Actions runs the tests on PHP 8.5 too, and the job with the latest dependencies
+  on PHP 8.5 instead of 8.4.
+
 ## [4.8.0] - 2026-11-01
 
 ### Added
diff --git a/SETUP.md b/SETUP.md
index 496081e6..9e1e2ea1 100644
--- a/SETUP.md
+++ b/SETUP.md
@@ -1,7 +1,7 @@
 # FormHandler – Development setup
 
 FormHandler is developed and tested with **PHP 8.2 in a Docker container**. You do
-not need a local PHP installation. GitHub Actions runs the tests on PHP 8.2, 8.3 and 8.4.
+not need a local PHP installation. GitHub Actions runs the tests on PHP 8.2, 8.3, 8.4 and 8.5.
 
 ## Requirements
 
@@ -82,7 +82,7 @@ Then open <http://localhost:8088/examples/>. Another port: `FH_WEB_PORT=8090 doc
 
 | Workflow | File | Runs |
 |---|---|---|
-| PHPUnit | `.github/workflows/phpunit.yml` | tests with coverage on PHP 8.2, 8.3 and 8.4 |
+| PHPUnit | `.github/workflows/phpunit.yml` | tests with coverage on PHP 8.2, 8.3, 8.4 and 8.5 |
 | PHPStan | `.github/workflows/phpstan.yml` | static analysis on PHP 8.2 |
 | Examples | `.github/workflows/examples.yml` | requests every example page on the PHP built-in server |
 
diff --git a/src/fields/class.UploadField.php b/src/fields/class.UploadField.php
index 6891ae6f..f266660a 100644
--- a/src/fields/class.UploadField.php
+++ b/src/fields/class.UploadField.php
@@ -540,12 +540,12 @@ public function isValid()
                 // does build in function exists for retrieving the mime type of the file?
                 // if so, get the type of the mime from that function (more secure)
                 // otherwise, use the one from the browser
-                // as of php 5.3 mime_content_type is deprecated, use finfo_open instead
-                if (function_exists('finfo_open'))
+                // as of php 5.3 mime_content_type is deprecated, use finfo instead
+                // (the object is freed by itself, finfo_close() is deprecated as of php 8.5)
+                if (class_exists('finfo'))
                 {
-                    $finfo = finfo_open(FILEINFO_MIME);
-                    $sTypeRaw = finfo_file($finfo, $aFile['tmp_name']);
-                    finfo_close($finfo);
+                    $finfo = new finfo(FILEINFO_MIME);
+                    $sTypeRaw = $finfo->file($aFile['tmp_name']);
                     list($sType) = preg_split('/;/', $sTypeRaw);
                 }
                 else
diff --git a/src/includes/class.ImageConverter.php b/src/includes/class.ImageConverter.php
index aaed1ce4..35c333bb 100644
--- a/src/includes/class.ImageConverter.php
+++ b/src/includes/class.ImageConverter.php
@@ -185,9 +185,9 @@ public function doResize($sDestination, $iNewWidth, $iNewHeight)
                 $this->_aSize[1] = $iNewHeight;
             }
 
-            // clean up
-            ImageDestroy($rOrg);
-            ImageDestroy($rImgResized);
+            // clean up (GD images are objects since php 8.0, imagedestroy() is deprecated as of php 8.5)
+            unset($rOrg);
+            unset($rImgResized);
         }
     }
 
@@ -251,7 +251,7 @@ public function doMerge($sStamp, $sAlign, $sValign, $aTransparant = null)
 
             // Copy the current file to the new one
             ImageCopy($rImgDest, $rImgSrc, 0, 0, 0, 0, $this->_aSize[0], $this->_aSize[1]);
-            ImageDestroy($rImgSrc);
+            unset($rImgSrc);
 
             // get the new position for the stamp
             $x = ImageSX($rImgStamp);
@@ -264,11 +264,11 @@ public function doMerge($sStamp, $sAlign, $sValign, $aTransparant = null)
             //ImageCopy( $rImgDest, $rImgStamp, $posX, $posY, 0, 0, $x, $y );  # transparant isnt working!
             //ImageCopyResampled( $rImgDest, $rImgStamp, 0, 0, $x, $y, $x, $y ); # transparant isnt working!
 
-            ImageDestroy($rImgStamp);
+            unset($rImgStamp);
 
             // Save the new image
             $this->_saveImage($rImgDest, $this->_sImage, 100);
-            ImageDestroy($rImgDest);
+            unset($rImgDest);
         }
         else
         {