diff --git a/libs/openFrameworks/gl/ofMaterial.h b/libs/openFrameworks/gl/ofMaterial.h
index c75c1d4ddf2..14c0de49df0 100644
--- a/libs/openFrameworks/gl/ofMaterial.h
+++ b/libs/openFrameworks/gl/ofMaterial.h
@@ -7,6 +7,7 @@
 #define GLM_ENABLE_EXPERIMENTAL
 #include <glm/fwd.hpp>
 #include <glm/vec2.hpp>
+#include <glm/mat4x4.hpp>
 
 #include <unordered_map>