diff --git a/src/Support/ClassLoader.php b/src/Support/ClassLoader.php
index 1a7673813..f46a98aa4 100644
--- a/src/Support/ClassLoader.php
+++ b/src/Support/ClassLoader.php
@@ -33,6 +33,11 @@ class ClassLoader
      */
     public $manifest = [];
 
+    /**
+     * @var array unknownClasses cache
+     */
+    protected $unknownClasses = [];
+
     /**
      * @var bool manifestDirty if manifest needs to be written
      */
@@ -68,6 +73,10 @@ public function __construct(Filesystem $files, string $basePath)
      */
     public function load($class): bool
     {
+        if (!str_contains($class, '\\')) {
+            return false;
+        }
+
         if (
             isset($this->manifest[$class]) &&
             is_file($fullPath = $this->basePath.DIRECTORY_SEPARATOR.$this->manifest[$class])
@@ -76,6 +85,10 @@ public function load($class): bool
             return true;
         }
 
+        if (isset($this->unknownClasses[$class])) {
+            return false;
+        }
+
         [$lowerClass, $upperClass] = $this->normalizeClass($class);
 
         // Load namespaces
@@ -94,6 +107,8 @@ public function load($class): bool
             }
         }
 
+        $this->unknownClasses[$class] = true;
+
         return false;
     }
 
@@ -150,7 +165,7 @@ public function register(): void
 
         $this->registered = spl_autoload_register(function($class) {
             $this->load($class);
-        }, true, true);
+        });
     }
 
     /**