diff --git a/src/Core/Injector/InjectionCreator.php b/src/Core/Injector/InjectionCreator.php
index 0c70e3b23..ad91f11d2 100644
--- a/src/Core/Injector/InjectionCreator.php
+++ b/src/Core/Injector/InjectionCreator.php
@@ -2,18 +2,36 @@
 
 namespace SilverStripe\Core\Injector;
 
+use InvalidArgumentException;
+
 /**
  * A class for creating new objects by the injector.
  */
 class InjectionCreator implements Factory
 {
+    /**
+     * Create a new instance of a class
+     *
+     * Passing an object for $class will result from using an anonymous class in unit testing, e.g.
+     * Injector::inst()->load([SomeClass::class => ['class' => new class { ... }]]);
+     *
+     * @param string|object $class - string: The FQCN of the class, object: A class instance
+     */
     public function create($class, array $params = [])
     {
-        if (!class_exists($class ?? '')) {
+        if (is_object($class ?? '')) {
+            $class = get_class($class);
+        }
+        if (!is_string($class ?? '')) {
+            throw new InvalidArgumentException('$class parameter must be a string or an object');
+        }
+        if (!class_exists($class)) {
             throw new InjectorNotFoundException("Class {$class} does not exist");
         }
+
         // Ensure there are no string keys as they cannot be unpacked with the `...` operator
-        $values = array_values($params ?? []);
+        $values = array_values($params);
+
         return new $class(...$values);
     }
 }
diff --git a/tests/php/Core/Injector/InjectorTest.php b/tests/php/Core/Injector/InjectorTest.php
index b06b0fc87..85aa7a3ff 100644
--- a/tests/php/Core/Injector/InjectorTest.php
+++ b/tests/php/Core/Injector/InjectorTest.php
@@ -1155,4 +1155,27 @@ class InjectorTest extends SapphireTest
         Injector::unnest();
         $this->nestingLevel--;
     }
+
+    public function testAnonymousClass()
+    {
+        Injector::inst()->load([
+            'Some\\Project\\Class' => [
+                // the php anonymous class syntax will instantiate a new anonymous class object, with ('abc')
+                // passed to the constructor
+                'class' => new class ('abc') {
+                    private string $property;
+                    public function __construct(string $value)
+                    {
+                        $this->property = $value;
+                    }
+                    public function foo(): string
+                    {
+                        return $this->property;
+                    }
+                }
+            ],
+        ]);
+        // assert that Injector creates a new instance of the anonymous class, with ('def') passed to the constructor
+        $this->assertSame('def', Injector::inst()->create('Some\\Project\\Class', 'def')->foo());
+    }
 }