diff --git a/notimpl/readonly.cpp b/notimpl/readonly.cpp
index 1ae2b30..94d1702 100644
--- a/notimpl/readonly.cpp
+++ b/notimpl/readonly.cpp
@@ -18,6 +18,9 @@
 
 #include <stdexcept>
 
+namespace pid_control
+{
+
 void ReadOnly::write(double value)
 {
     throw std::runtime_error("Not supported.");
@@ -27,3 +30,5 @@
 {
     return;
 }
+
+} // namespace pid_control
diff --git a/notimpl/readonly.hpp b/notimpl/readonly.hpp
index 6a48f0b..3a2c806 100644
--- a/notimpl/readonly.hpp
+++ b/notimpl/readonly.hpp
@@ -4,6 +4,9 @@
 
 #include "interfaces.hpp"
 
+namespace pid_control
+{
+
 class ReadOnly : public WriteInterface
 {
   public:
@@ -21,3 +24,5 @@
 
     void write(double value) override;
 };
+
+} // namespace pid_control
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
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