diff --git a/src/viewport_func.h b/src/viewport_func.h
--- a/src/viewport_func.h
+++ b/src/viewport_func.h
@@ -22,8 +22,8 @@ void SetSelectionRed(bool);
 
 void DeleteWindowViewport(Window *w);
 void InitializeWindowViewport(Window *w, int x, int y, int width, int height, uint32 follow_flags, ZoomLevel zoom);
-ViewPort *IsPtInWindowViewport(const Window *w, int x, int y);
-Point TranslateXYToTileCoord(const ViewPort *vp, int x, int y, bool clamp_to_map = true);
+Viewport *IsPtInWindowViewport(const Window *w, int x, int y);
+Point TranslateXYToTileCoord(const Viewport *vp, int x, int y, bool clamp_to_map = true);
 Point GetTileBelowCursor();
 void UpdateViewportPosition(Window *w);
 
@@ -33,7 +33,7 @@ bool DoZoomInOutWindow(ZoomStateChange h
 void ZoomInOrOutToCursorWindow(bool in, Window * w);
 Point GetTileZoomCenterWindow(bool in, Window * w);
 void FixTitleGameZoom();
-void HandleZoomMessage(Window *w, const ViewPort *vp, byte widget_zoom_in, byte widget_zoom_out);
+void HandleZoomMessage(Window *w, const Viewport *vp, byte widget_zoom_in, byte widget_zoom_out);
 
 /**
  * Zoom a viewport as far as possible in the given direction.
@@ -58,12 +58,12 @@ void ViewportAddString(const DrawPixelIn
 void StartSpriteCombine();
 void EndSpriteCombine();
 
-bool HandleViewportClicked(const ViewPort *vp, int x, int y);
+bool HandleViewportClicked(const Viewport *vp, int x, int y);
 void SetRedErrorSquare(TileIndex tile);
 void SetTileSelectSize(int w, int h);
 void SetTileSelectBigSize(int ox, int oy, int sx, int sy);
 
-void ViewportDoDraw(const ViewPort *vp, int left, int top, int right, int bottom);
+void ViewportDoDraw(const Viewport *vp, int left, int top, int right, int bottom);
 
 bool ScrollWindowToTile(TileIndex tile, Window *w, bool instant = false);
 bool ScrollWindowTo(int x, int y, int z, Window *w, bool instant = false);
@@ -91,7 +91,7 @@ static inline void MarkTileDirtyByTile(T
 	MarkTileDirtyByTile(tile, bridge_level_offset, TileHeight(tile));
 }
 
-Point GetViewportStationMiddle(const ViewPort *vp, const Station *st);
+Point GetViewportStationMiddle(const Viewport *vp, const Station *st);
 
 struct Station;
 struct Town;