diff --git a/src/exception.cpp b/src/exception.cpp
index bc72783..8814f53 100644
--- a/src/exception.cpp
+++ b/src/exception.cpp
@@ -251,6 +251,7 @@ namespace fc
       } catch( ... ) {
          ss << "<- exception in to_string.\n";
       }
+      return ss.str();
    }
 
    [[noreturn]] void exception_factory::rethrow( const exception& e )const