diff --git a/src/lib/sim/Command.h b/src/lib/sim/Command.h
index b91c426..d3c4f2f 100644
--- a/src/lib/sim/Command.h
+++ b/src/lib/sim/Command.h
@@ -13,7 +13,7 @@
 #include "Rotation.h"
 #include "ShipLayout.h"
 
-class GameConfig;
+struct GameConfig;
 
 // Player intent, resolved to domain ids / tile coordinates and serializable, that
 // mutates the simulation. Every sim mutation during play flows through a Command