diff --git a/core/Object.php b/core/Object.php
index b84516607..2e49fbd76 100755
--- a/core/Object.php
+++ b/core/Object.php
@@ -538,7 +538,12 @@ abstract class Object {
 		
 		// load statics now for DataObject classes
 		if(ClassInfo::is_subclass_of($class, 'DataObject')) {
-			DataObjectDecorator::load_extra_statics($class, $extension);
+			if(is_subclass_of($extensionClass, 'DataObjectDecorator')) {
+				DataObjectDecorator::load_extra_statics($class, $extension);
+			}
+			else {
+				user_error("$extensionClass cannot be applied to $class without being a DataObjectDecorator", E_USER_ERROR);
+			}
 		}
 	}
 
@@ -550,12 +555,26 @@ abstract class Object {
 		// _cache_statics_prepared setting must come first to prevent infinite loops when we call
 		// get_static below
 		self::$_cache_statics_prepared[$class] = true;
-
+		
 		// load statics now for DataObject classes
 		if(is_subclass_of($class, 'DataObject')) {
 			$extensions = Object::uninherited_static($class, 'extensions');
-			if($extensions) foreach($extensions as $extension) {
-				DataObjectDecorator::load_extra_statics($class, $extension);
+			
+			if($extensions) {
+				foreach($extensions as $extension) {
+					$extensionClass = $extension;
+					
+					if(preg_match('/^([^(]*)/', $extension, $matches)) {
+						$extensionClass = $matches[1];
+					}
+					
+					if(is_subclass_of($extensionClass, 'DataObjectDecorator')) {
+						DataObjectDecorator::load_extra_statics($class, $extension);
+					}
+					else {
+						user_error("$extensionClass cannot be applied to $class without being a DataObjectDecorator", E_USER_ERROR);
+					}
+				}
 			}
 		}
 	}
diff --git a/tests/api/RestfulServiceTest.php b/tests/api/RestfulServiceTest.php
index 76f943a4a..0da14a7a0 100644
--- a/tests/api/RestfulServiceTest.php
+++ b/tests/api/RestfulServiceTest.php
@@ -99,9 +99,9 @@ class RestfulServiceTest extends SapphireTest {
 	}
 	
 	function testHttpErrorWithoutCache() {
-		$connection = new RestfulService(Director::absoluteBaseURL(), 0);
+		$connection = new RestfulServiceTest_MockRestfulService(Director::absoluteBaseURL(), 0);
 		$response = $connection->request('RestfulServiceTest_Controller/httpErrorWithoutCache?usetestmanifest=1&flush=1');
-		
+
 		$this->assertEquals(400, $response->getStatusCode());
 		$this->assertFalse($response->getCachedBody());
 		$this->assertContains("<error>HTTP Error</error>", $response->getBody());
@@ -271,5 +271,4 @@ class RestfulServiceTest_MockRestfulService extends RestfulService {
 
 		return $response;
 	}
-}
-?>
+}
\ No newline at end of file