diff --git a/system/Autoloader/FileLocator.php b/system/Autoloader/FileLocator.php
index bc18bd31b980..6f241e847be3 100644
--- a/system/Autoloader/FileLocator.php
+++ b/system/Autoloader/FileLocator.php
@@ -273,12 +273,15 @@ public function findQualifiedNameFromPath(string $path)
             }
 
             if (mb_strpos($path, $namespace['path']) === 0) {
-                $className = '\\' . $namespace['prefix'] . '\\' .
-                        ltrim(str_replace(
+                $className = $namespace['prefix'] . '\\' .
+                    ltrim(
+                        str_replace(
                             '/',
                             '\\',
                             mb_substr($path, mb_strlen($namespace['path']))
-                        ), '\\');
+                        ),
+                        '\\'
+                    );
 
                 // Remove the file extension (.php)
                 $className = mb_substr($className, 0, -4);
diff --git a/tests/system/Autoloader/FileLocatorTest.php b/tests/system/Autoloader/FileLocatorTest.php
index 1cf32cfa5ad1..0d084280f520 100644
--- a/tests/system/Autoloader/FileLocatorTest.php
+++ b/tests/system/Autoloader/FileLocatorTest.php
@@ -278,7 +278,7 @@ public function testListFilesWithoutPath(): void
     public function testFindQNameFromPathSimple(): void
     {
         $ClassName = $this->locator->findQualifiedNameFromPath(SYSTEMPATH . 'HTTP/Header.php');
-        $expected  = '\\' . Header::class;
+        $expected  = Header::class;
 
         $this->assertSame($expected, $ClassName);
     }
diff --git a/user_guide_src/source/changelogs/v4.5.0.rst b/user_guide_src/source/changelogs/v4.5.0.rst
index b64f9b3997a7..89910fa84f3d 100644
--- a/user_guide_src/source/changelogs/v4.5.0.rst
+++ b/user_guide_src/source/changelogs/v4.5.0.rst
@@ -33,6 +33,8 @@ Others
 - **Logger:** The :php:func:`log_message()` function and the logger methods in
   ``CodeIgniter\Log\Logger`` now do not return ``bool`` values. The return types
   have been fixed to ``void`` to follow the PSR-3 interface.
+- **Autoloader:** The prefix ``\`` in the fully qualified classname returned by
+  ``FileLocator::findQualifiedNameFromPath()`` has been removed.
 
 Interface Changes
 =================
diff --git a/user_guide_src/source/installation/upgrade_450.rst b/user_guide_src/source/installation/upgrade_450.rst
index 240203f4b888..0a868831503c 100644
--- a/user_guide_src/source/installation/upgrade_450.rst
+++ b/user_guide_src/source/installation/upgrade_450.rst
@@ -72,6 +72,14 @@ reversed.
         Previous: route1 → route2 → filter1 → filter2
              Now: route2 → route1 → filter2 → filter1
 
+FileLocator::findQualifiedNameFromPath()
+========================================
+
+In previous versions, ``FileLocator::findQualifiedNameFromPath()`` returns Fully
+Qualified Classnames with a leading ``\``. Now the leading ``\`` has been removed.
+
+If you have code that expects a leading ``\``, fix it.
+
 Removed Deprecated Items
 ========================