diff --git a/notimpl/writeonly.hpp b/notimpl/writeonly.hpp
index ba7c0c4..c3b5323 100644
--- a/notimpl/writeonly.hpp
+++ b/notimpl/writeonly.hpp
@@ -3,6 +3,9 @@
 
 #include "interfaces.hpp"
 
+namespace pid_control
+{
+
 class WriteOnly : public ReadInterface
 {
   public:
@@ -11,3 +14,5 @@
 
     ReadReturn read(void) override;
 };
+
+} // namespace pid_control