diff --git a/src/openrct2-ui/WindowManager.h b/src/openrct2-ui/WindowManager.h
index aabb324c50..0f13c8579f 100644
--- a/src/openrct2-ui/WindowManager.h
+++ b/src/openrct2-ui/WindowManager.h
@@ -7,6 +7,8 @@
  * OpenRCT2 is licensed under the GNU General Public License version 3.
  *****************************************************************************/
 
+#pragma once
+
 #include <openrct2/common.h>
 
 namespace OpenRCT2::Ui
diff --git a/src/openrct2-ui/drawing/BitmapReader.h b/src/openrct2-ui/drawing/BitmapReader.h
index cb239afff3..4328b01c15 100644
--- a/src/openrct2-ui/drawing/BitmapReader.h
+++ b/src/openrct2-ui/drawing/BitmapReader.h
@@ -7,4 +7,6 @@
  * OpenRCT2 is licensed under the GNU General Public License version 3.
  *****************************************************************************/
 
+#pragma once
+
 void RegisterBitmapReader();
diff --git a/src/openrct2/drawing/ImageImporter.h b/src/openrct2/drawing/ImageImporter.h
index d1faccceda..b89afe5cee 100644
--- a/src/openrct2/drawing/ImageImporter.h
+++ b/src/openrct2/drawing/ImageImporter.h
@@ -7,6 +7,8 @@
  * OpenRCT2 is licensed under the GNU General Public License version 3.
  *****************************************************************************/
 
+#pragma once
+
 #include "../core/Imaging.h"
 #include "Drawing.h"