diff --git a/src/inventorymanager.h b/src/inventorymanager.h
index 55e8f8402..52377f9a4 100644
--- a/src/inventorymanager.h
+++ b/src/inventorymanager.h
@@ -103,6 +103,7 @@ struct InventoryAction
 	virtual void apply(InventoryManager *mgr, ServerActiveObject *player,
 			IGameDef *gamedef) = 0;
 	virtual void clientApply(InventoryManager *mgr, IGameDef *gamedef) = 0;
+	virtual ~InventoryAction() {};
 };
 
 struct IMoveAction : public InventoryAction
diff --git a/src/player.h b/src/player.h
index 085a4a15a..d62fb6111 100644
--- a/src/player.h
+++ b/src/player.h
@@ -30,7 +30,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 class Map;
 class IGameDef;
-class CollisionInfo;
+struct CollisionInfo;
 
 class Player
 {
diff --git a/src/scriptapi.h b/src/scriptapi.h
index 500a9ab99..df8ae344e 100644
--- a/src/scriptapi.h
+++ b/src/scriptapi.h
@@ -30,7 +30,7 @@ class ServerActiveObject;
 class ServerRemotePlayer;
 typedef struct lua_State lua_State;
 struct LuaEntityProperties;
-class ItemStack;
+struct ItemStack;
 struct PointedThing;
 //class IGameDef;
 
diff --git a/src/serverobject.h b/src/serverobject.h
index 94ceb4895..380bf7302 100644
--- a/src/serverobject.h
+++ b/src/serverobject.h
@@ -42,7 +42,7 @@ Some planning
 */
 
 class ServerEnvironment;
-class ItemStack;
+struct ItemStack;
 class Player;
 struct ToolDiggingProperties;