diff --git a/system/Autoloader/Autoloader.php b/system/Autoloader/Autoloader.php
index 520e669be685..311428fe4165 100644
--- a/system/Autoloader/Autoloader.php
+++ b/system/Autoloader/Autoloader.php
@@ -328,7 +328,7 @@ private function loadComposerNamespaces(ClassLoader $composer): void
             $newPaths[rtrim($key, '\\ ')] = $value;
         }
 
-        $this->prefixes = array_merge($this->prefixes, $newPaths);
+        $this->addNamespace($newPaths);
     }
 
     private function loadComposerClassmap(ClassLoader $composer): void
diff --git a/tests/system/Autoloader/AutoloaderTest.php b/tests/system/Autoloader/AutoloaderTest.php
index 82e0307affad..1279910d2289 100644
--- a/tests/system/Autoloader/AutoloaderTest.php
+++ b/tests/system/Autoloader/AutoloaderTest.php
@@ -233,6 +233,23 @@ public function testFindsComposerRoutes()
         $this->assertArrayHasKey('Laminas\\Escaper', $namespaces);
     }
 
+    public function testComposerNamespaceDoesNotOverwriteConfigAutoloadPsr4()
+    {
+        $config       = new Autoload();
+        $config->psr4 = [
+            'Psr\Log' => '/Config/Autoload/Psr/Log/',
+        ];
+        $modules                     = new Modules();
+        $modules->discoverInComposer = true;
+
+        $this->loader = new Autoloader();
+        $this->loader->initialize($config, $modules);
+
+        $namespaces = $this->loader->getNamespace();
+        $this->assertSame('/Config/Autoload/Psr/Log/', $namespaces['Psr\Log'][0]);
+        $this->assertStringContainsString(VENDORPATH, $namespaces['Psr\Log'][1]);
+    }
+
     public function testFindsComposerRoutesWithComposerPathNotFound()
     {
         $composerPath = COMPOSER_PATH;