diff --git a/src/signal/signal-cast-helper.cpp b/src/signal/signal-cast-helper.cpp
index fd20f7e7f667c5901ba080afe12616733b117a7c..37b90792ce4d17566eb112a8be8b360e509eb72c 100644
--- a/src/signal/signal-cast-helper.cpp
+++ b/src/signal/signal-cast-helper.cpp
@@ -82,6 +82,7 @@ DefaultCastRegisterer<bool> bool_reg;
 DefaultCastRegisterer<dynamicgraph::Vector> vectorCastRegisterer;
 DefaultCastRegisterer<dynamicgraph::Matrix> matrixCastRegisterer;
 DefaultCastRegisterer<boost::posix_time::ptime> ptimeCastRegisterer;
+DefaultCastRegisterer <std::string> stringCastRegisterer;
 } // end of anonymous namespace.
 
 } // namespace dynamicgraph