diff --git a/tempest/matrix/C34Matrix.cpp b/tempest/matrix/C34Matrix.cpp
index b11b8b5..02206d0 100644
--- a/tempest/matrix/C34Matrix.cpp
+++ b/tempest/matrix/C34Matrix.cpp
@@ -2,6 +2,7 @@
 #include "tempest/vector/C3Vector.hpp"
 #include "tempest/matrix/C33Matrix.hpp"
 #include "tempest/quaternion/C4Quaternion.hpp"
+#include "tempest/math/CMath.hpp"
 
 
 C34Matrix C34Matrix::Rotation(float angle, const C3Vector& axis, bool unit) {