diff --git a/pid/fan.hpp b/pid/fan.hpp
index 7792d04..a16942b 100644
--- a/pid/fan.hpp
+++ b/pid/fan.hpp
@@ -1,9 +1,14 @@
 
 #pragma once
 
+namespace pid_control
+{
+
 enum class FanSpeedDirection
 {
     DOWN,
     UP,
     NEUTRAL, /* not sure this will ever happen, but for completeness. */
 };
+
+}