diff --git a/src/heightmap.h b/src/heightmap.h
--- a/src/heightmap.h
+++ b/src/heightmap.h
@@ -12,6 +12,8 @@
 #ifndef HEIGHTMAP_H
 #define HEIGHTMAP_H
 
+#include "fileio_type.h"
+
 /**
  * Order of these enums has to be the same as in lang/english.txt
  * Otherwise you will get inconsistent behaviour.
@@ -21,8 +23,8 @@ enum HeightmapRotation {
 	HM_CLOCKWISE,         ///< Rotate the map clockwise 45 degrees
 };
 
-bool GetHeightmapDimensions(char *filename, uint *x, uint *y);
-void LoadHeightmap(char *filename);
+bool GetHeightmapDimensions(DetailedFileType dft, const char *filename, uint *x, uint *y);
+void LoadHeightmap(DetailedFileType dft, const char *filename);
 void FlatEmptyWorld(byte tile_height);
 void FixSlopes();