diff --git a/notimpl/writeonly.cpp b/notimpl/writeonly.cpp
index 9fc99fd..de354e6 100644
--- a/notimpl/writeonly.cpp
+++ b/notimpl/writeonly.cpp
@@ -18,7 +18,12 @@
 
 #include <stdexcept>
 
+namespace pid_control
+{
+
 ReadReturn WriteOnly::read(void)
 {
     throw std::runtime_error("Not supported.");
 }
+
+} // namespace pid_control