diff --git a/include/smath/smath.hpp b/include/smath/smath.hpp
index 9097704..2f45b80 100644
--- a/include/smath/smath.hpp
+++ b/include/smath/smath.hpp
@@ -17,6 +17,7 @@
  *
  * You can define the following macros to change functionality:
  * - SMATH_IMPLICIT_CONVERSIONS
+ * - SMATH_ANGLE_UNIT (=rad, =deg, =turns)
  */
 
 #pragma once