diff --git a/src/ProtocolBuffers.Test/AbstractMessageTest.cs b/src/ProtocolBuffers.Test/AbstractMessageTest.cs
index bef5052..a502a6c 100644
--- a/src/ProtocolBuffers.Test/AbstractMessageTest.cs
+++ b/src/ProtocolBuffers.Test/AbstractMessageTest.cs
@@ -133,6 +133,7 @@
             byte[] bytes = TestUtil.GetPackedSet().ToByteArray();
             ExtensionRegistry registry = ExtensionRegistry.CreateInstance();
             UnitTestProtoFile.RegisterAllExtensions(registry);
+            UnitTestExtrasProtoFile.RegisterAllExtensions(registry);
             TestUnpackedExtensions message = TestUnpackedExtensions.ParseFrom(bytes, registry);
             TestUtil.AssertUnpackedExtensionsSet(message);
         }