diff --git a/src/viewport_func.h b/src/viewport_func.h
--- a/src/viewport_func.h
+++ b/src/viewport_func.h
@@ -43,7 +43,7 @@ void HandleZoomMessage(Window *w, const 
  * @param w   Window owning the viewport.
  * @pre \a how should not be #ZOOM_NONE.
  */
-static inline void MaxZoomInOut(ZoomStateChange how, Window *w)
+inline void MaxZoomInOut(ZoomStateChange how, Window *w)
 {
 	while (DoZoomInOutWindow(how, w)) {};
 }
@@ -88,7 +88,7 @@ void MarkTileDirtyByTile(TileIndex tile,
  * @param bridge_level_offset Height of bridge on tile to also mark dirty. (Height level relative to north corner.)
  * @ingroup dirty
  */
-static inline void MarkTileDirtyByTile(TileIndex tile, int bridge_level_offset = 0)
+inline void MarkTileDirtyByTile(TileIndex tile, int bridge_level_offset = 0)
 {
 	MarkTileDirtyByTile(tile, bridge_level_offset, TileHeight(tile));
 }