diff --git a/include/MetroidPrime/CStateManager.hpp b/include/MetroidPrime/CStateManager.hpp
index 7ab61b31..e1e86740 100644
--- a/include/MetroidPrime/CStateManager.hpp
+++ b/include/MetroidPrime/CStateManager.hpp
@@ -35,6 +35,7 @@ class CWorldTransManager;
 class CEntity;
 class CMazeState;
 class CRayCastResult;
+class CMaterialFilter;
 
 namespace SL {
 class CSortedListManager;