diff --git a/test/adaptor_test/type_erased_transformed.cpp b/test/adaptor_test/type_erased_transformed.cpp
index 20a8696..1b38261 100644
--- a/test/adaptor_test/type_erased_transformed.cpp
+++ b/test/adaptor_test/type_erased_transformed.cpp
@@ -28,6 +28,7 @@ typedef boost::any_range<
 
 struct get_fn
 {
+    typedef boost::int32_t result_type;
     boost::int32_t operator()(const MockType& val) const
     {
         return val.get();