diff --git a/phpdotnet/phd/Config.php b/phpdotnet/phd/Config.php
index 8c561c63..defc50c6 100644
--- a/phpdotnet/phd/Config.php
+++ b/phpdotnet/phd/Config.php
@@ -57,6 +57,15 @@ class Config
     public string $phpwebSourcesFilename = '';
     public string $phpwebHistoryFilename = '';
     
+    private const NON_SERIALIZABLE_PROPERTIES = [
+        "copyright",
+        "indexCache",
+        "phpErrorOutput",
+        "userErrorOutput",
+        "phdInfoOutput",
+        "phdWarningOutput",
+    ];
+    
     public function __construct() {
         $this->copyright = 'Copyright(c) 2007-'  . \date('Y') . ' The PHP Documentation Group';
         
@@ -76,6 +85,10 @@ public function init(array $configOptions): void {
                 throw new \Exception("Invalid option supplied: $option");
             }
             
+            if (\in_array($option, self::NON_SERIALIZABLE_PROPERTIES, true)) {
+                continue;
+            }
+            
             $this->$option = $value;
         }
         
@@ -83,12 +96,18 @@ public function init(array $configOptions): void {
     }
 
     /**
-     * Returns all configuration options and their values
+     * Returns all serializable configuration options and their values
      * 
      * @return array<string, mixed>
      */
-    public function getAllFiltered(): array {
-        return \get_object_vars($this);
+    public function getAllSerializableProperties(): array {
+        $object_vars = \get_object_vars($this);
+        
+        foreach (self::NON_SERIALIZABLE_PROPERTIES as $property) {
+            unset($object_vars[$property]);
+        }
+        
+        return $object_vars;
     }
 
     /**
diff --git a/render.php b/render.php
index dbd451fa..be2d0c06 100644
--- a/render.php
+++ b/render.php
@@ -74,7 +74,7 @@
 
 if ($config->saveConfig) {
     $outputHandler->v("Writing the config file", VERBOSE_MESSAGES);
-    file_put_contents("phd.config.php", "<?php\nreturn " . var_export($config->getAllFiltered(), 1) . ";");
+    file_put_contents("phd.config.php", "<?php\nreturn " . var_export($config->getAllSerializableProperties(), 1) . ";");
 }
 
 if ($config->quit) {
diff --git a/tests/GH-225.phpt b/tests/GH-225.phpt
new file mode 100644
index 00000000..bf418192
--- /dev/null
+++ b/tests/GH-225.phpt
@@ -0,0 +1,31 @@
+--TEST--
+GH-225 - SaveConfig tries to overwrite readonly property
+--ARGS--
+--docbook tests/data/bug-GH-225.xml --quit
+--FILE--
+<?php
+namespace phpdotnet\phd;
+
+if (!\file_exists(__DIR__ . "/../output/")) {
+    \mkdir(__DIR__ . "/../output/", 0777, true);
+}
+
+if (\file_exists(__DIR__ . "/../phd.config.php")) {
+    \unlink(__DIR__ . "/../phd.config.php");
+}
+
+\file_put_contents(__DIR__ . "/../phd.config.php",    
+"<?php
+return array (
+  'copyright' => 'Should not be imported',
+);");
+
+require_once __DIR__ . "/../render.php";
+?>
+--CLEAN--
+<?php
+\unlink(__DIR__ . "/../phd.config.php");
+\rmdir(__DIR__ . "/../output/");
+?>
+--EXPECTF--
+%s[%d:%d:%d - Heads up              ]%s Loaded config from existing file
diff --git a/tests/data/bug-GH-225.xml b/tests/data/bug-GH-225.xml
new file mode 100644
index 00000000..b62ca013
--- /dev/null
+++ b/tests/data/bug-GH-225.xml
@@ -0,0 +1,2 @@
+<test>
+</test>
\ No newline at end of file