diff --git a/include/boost/mp11/algorithm.hpp b/include/boost/mp11/algorithm.hpp
index 996a61f..dbd3ef5 100644
--- a/include/boost/mp11/algorithm.hpp
+++ b/include/boost/mp11/algorithm.hpp
@@ -117,15 +117,19 @@ template<class... L> struct mp_same_size_2: mp_defer<mp_same_size_1, L...> {};
 
 #endif
 
+struct list_size_mismatch
+{
+};
+
 } // namespace detail
 
 #if BOOST_WORKAROUND( BOOST_MSVC, == 1900 ) || BOOST_WORKAROUND( BOOST_GCC, < 40800 )
 
-template<template<class...> class F, class... L> using mp_transform = typename mp_if<typename detail::mp_same_size_2<L...>::type, detail::mp_transform_impl<F, L...>>::type;
+template<template<class...> class F, class... L> using mp_transform = typename mp_if<typename detail::mp_same_size_2<L...>::type, detail::mp_transform_impl<F, L...>, detail::list_size_mismatch>::type;
 
 #else
 
-template<template<class...> class F, class... L> using mp_transform = typename mp_if<mp_same<mp_size<L>...>, detail::mp_transform_impl<F, L...>>::type;
+template<template<class...> class F, class... L> using mp_transform = typename mp_if<mp_same<mp_size<L>...>, detail::mp_transform_impl<F, L...>, detail::list_size_mismatch>::type;
 
 #endif