diff --git a/README.md b/README.md
index da483a3..9c48fcf 100644
--- a/README.md
+++ b/README.md
@@ -43,11 +43,11 @@ $explorer = new GlobClassExplorer('\\This\\Namespace\\Only\\', $psr16Cache, $cac
 
 You can also get a class map using the `getClassMap` method.
 A class map is an array associating the name of the classes found (in key), to the file they are 
-linked to (a `SplFileInfo` in value).
+linked to (the real path of the file).
 
 ```php
 $classMap = $explorer->getClassMap();
-foreach ($classMap as $class => $fileInfo) {
-    echo 'Class '.$class.' found in file '.$fileInfo->getPathname();
+foreach ($classMap as $class => $file) {
+    echo 'Class '.$class.' found in file '.$file;
 }
 ```
diff --git a/composer.json b/composer.json
index b9b3769..c8520a3 100644
--- a/composer.json
+++ b/composer.json
@@ -15,7 +15,8 @@
     "require": {
     	"php": ">=7.1",
         "psr/simple-cache": "^1",
-        "mouf/classname-mapper": "^1"
+        "mouf/classname-mapper": "^1",
+        "ext-hash": "*"
     },
     "require-dev": {
         "php-coveralls/php-coveralls": "^2.1",
diff --git a/src/Glob/GlobClassExplorer.php b/src/Glob/GlobClassExplorer.php
index accc980..0c08c32 100644
--- a/src/Glob/GlobClassExplorer.php
+++ b/src/Glob/GlobClassExplorer.php
@@ -54,6 +54,10 @@ class GlobClassExplorer implements ClassExplorerInterface
      * @var string
      */
     private $rootPath;
+    /**
+     * @var string|null
+     */
+    private $key;
 
     public function __construct(string $namespace, CacheInterface $cache, ?int $cacheTtl = null, ?ClassNameMapper $classNameMapper = null, bool $recursive = true, ?string $rootPath = null)
     {
@@ -78,15 +82,17 @@ public function getClasses(): array
     /**
      * Returns an array mapping the fully qualified class name to the file path.
      *
-     * @return array<string,SplFileInfo>
+     * @return array<string,string>
      */
     public function getClassMap(): array
     {
-        $key = 'globClassExplorer_'.str_replace('\\', '_', $this->namespace);
-        $classes = $this->cache->get($key);
+        if ($this->key === null) {
+            $this->key = 'globClassExplorer_'.hash('md4', $this->namespace.'___'.$this->recursive.$this->rootPath);
+        }
+        $classes = $this->cache->get($this->key);
         if ($classes === null) {
             $classes = $this->doGetClassMap();
-            $this->cache->set($key, $classes, $this->cacheTtl);
+            $this->cache->set($this->key, $classes, $this->cacheTtl);
         }
         return $classes;
     }
@@ -94,7 +100,7 @@ public function getClassMap(): array
     /**
      * Returns an array of fully qualified class names, without the cache.
      *
-     * @return array<string,SplFileInfo>
+     * @return array<string,string>
      */
     private function doGetClassMap(): array
     {
@@ -115,7 +121,7 @@ private function doGetClassMap(): array
             foreach ($filesForDir as $file) {
                 // Trim the root directory name and the PHP extension
                 $fileTrimPrefixSuffix = \substr($file, $dirLen, -4);
-                $classes[$namespace.\str_replace('/', '\\', $fileTrimPrefixSuffix)] = $file;
+                $classes[$namespace.\str_replace('/', '\\', $fileTrimPrefixSuffix)] = $file->getRealPath();
             }
         }
         chdir($oldCwd);
diff --git a/tests/Glob/GlobClassExplorerTest.php b/tests/Glob/GlobClassExplorerTest.php
index a9b6110..0cd1565 100644
--- a/tests/Glob/GlobClassExplorerTest.php
+++ b/tests/Glob/GlobClassExplorerTest.php
@@ -47,6 +47,6 @@ public function testGetClassMap()
         $classMap = $explorer->getClassMap();
 
         $this->assertArrayHasKey(GlobClassExplorer::class, $classMap);
-        $this->assertSame('src/Glob/GlobClassExplorer.php', (string) $classMap[GlobClassExplorer::class]);
+        $this->assertStringEndsWith('src/Glob/GlobClassExplorer.php', (string) $classMap[GlobClassExplorer::class]);
     }
 }