diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6594e5d7..457d8a11 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,7 +19,7 @@ jobs:
         strategy:
             matrix:
                 php-version:
-                    - '7.4'
+                    - '8.1'
 
         steps:
             -
@@ -52,7 +52,7 @@ jobs:
         strategy:
             matrix:
                 php-version:
-                    - '7.4'
+                    - '8.1'
 
         steps:
             -
@@ -85,8 +85,7 @@ jobs:
         strategy:
             matrix:
                 php-version:
-                    - '7.4'
-                    - '8.0'
+                    - '8.1'
 
         steps:
             -
diff --git a/lib/Adapter/Composer/ComposerClassToFile.php b/lib/Adapter/Composer/ComposerClassToFile.php
index 96ca8333..8f4c7478 100644
--- a/lib/Adapter/Composer/ComposerClassToFile.php
+++ b/lib/Adapter/Composer/ComposerClassToFile.php
@@ -31,7 +31,7 @@ public function classToFileCandidates(ClassName $className): FilePathCandidates
 
         // order with the longest prefixes first
         uksort($candidates, function ($prefix1, $prefix2) {
-            return strlen($prefix2) <=> strlen($prefix1);
+            return strlen((string)$prefix2) <=> strlen((string)$prefix1);
         });
 
         // flatten to a single array
diff --git a/lib/Domain/ClassName.php b/lib/Domain/ClassName.php
index b1e37aee..1d55e1e2 100644
--- a/lib/Domain/ClassName.php
+++ b/lib/Domain/ClassName.php
@@ -22,7 +22,7 @@ public function __toString()
     public static function fromString(string $string): self
     {
         $new = new self();
-        $new->fullyQualifiedName = $string;
+        $new->fullyQualifiedName = ltrim($string, self::DEFAULT_NAMESPACE_SEPARATOR);
 
         return $new;
     }
diff --git a/tests/Integration/Simple/SimpleClassToFileTest.php b/tests/Integration/Simple/SimpleClassToFileTest.php
index a3b07381..6f5922e1 100644
--- a/tests/Integration/Simple/SimpleClassToFileTest.php
+++ b/tests/Integration/Simple/SimpleClassToFileTest.php
@@ -30,6 +30,15 @@ public function testClassToFile(): void
         ]), $candidates);
     }
 
+    public function testAbsoluteClassNameToFile(): void
+    {
+        $candidates = $this->classToFile->classToFileCandidates(ClassName::fromString('\\Acme\\Foobar'));
+
+        $this->assertEquals(FilePathCandidates::fromFilePaths([
+            FilePath::fromString(__DIR__ . '/../../Workspace/lib/Foobar.php')
+        ]), $candidates);
+    }
+
     public function testClassToFileInvalid(): void
     {
         $candidates = $this->classToFile->classToFileCandidates(
diff --git a/tests/Unit/ClassNameTest.php b/tests/Unit/ClassNameTest.php
index 6d85ddc4..e9eed364 100644
--- a/tests/Unit/ClassNameTest.php
+++ b/tests/Unit/ClassNameTest.php
@@ -24,6 +24,11 @@ public function provideBeginsWith()
                 'Foobar',
                 true,
             ],
+            [
+                '\\Foobar\\BarFoo',
+                'Foobar\\BarFoo',
+                true,
+            ],
             [
                 'Foobar\\BarFoo',
                 'Foobar\\BarFoo',