diff --git a/include/eigenpy/fwd.hpp b/include/eigenpy/fwd.hpp
index 629d9276a96f456927155e4148a460b17227be66..3bc5937d05caebcd8be7c367693144acb31364b1 100644
--- a/include/eigenpy/fwd.hpp
+++ b/include/eigenpy/fwd.hpp
@@ -1,6 +1,5 @@
 /*
- * Copyright 2014-2019, CNRS
- * Copyright 2018-2019, INRIA
+ * Copyright 2014-2020 CNRS INRIA
  */
 
 #ifndef __eigenpy_fwd_hpp__
@@ -27,4 +26,10 @@
 
 #include "eigenpy/expose.hpp"
 
+namespace eigenpy
+{
+  template<typename MatType> struct EigenToPy;
+  template<typename MatType> struct EigenFromPy;
+}
+
 #endif // ifndef __eigenpy_fwd_hpp__