diff --git a/notimpl/writeonly.cpp b/notimpl/writeonly.cpp
index de354e6..ef54cd5 100644
--- a/notimpl/writeonly.cpp
+++ b/notimpl/writeonly.cpp
@@ -16,6 +16,8 @@
 
 #include "writeonly.hpp"
 
+#include "interfaces.hpp"
+
 #include <stdexcept>
 
 namespace pid_control