Lite feature complete.
diff --git a/src/ProtocolBuffers.Test/ReflectionTester.cs b/src/ProtocolBuffers.Test/ReflectionTester.cs
index 32b6446..3e7ed39 100644
--- a/src/ProtocolBuffers.Test/ReflectionTester.cs
+++ b/src/ProtocolBuffers.Test/ReflectionTester.cs
@@ -213,7 +213,7 @@
ExtensionInfo extension = extensionRegistry[field.ContainingType, field.FieldNumber];
Assert.IsNotNull(extension);
Assert.IsNotNull(extension.DefaultInstance);
- return extension.DefaultInstance.WeakCreateBuilderForType();
+ return (IBuilder)extension.DefaultInstance.WeakCreateBuilderForType();
}
}