diff --git a/src/terraform_gui.cpp b/src/terraform_gui.cpp
--- a/src/terraform_gui.cpp
+++ b/src/terraform_gui.cpp
@@ -159,6 +159,8 @@ static const uint16 _terraform_keycodes[
 	'O',
 };
 
+void CcPlaySound1E(bool success, TileIndex tile, uint32 p1, uint32 p2);
+
 static void PlaceProc_BuyLand(TileIndex tile)
 {
 	DoCommandP(tile, 0, 0, CcPlaySound1E, CMD_PURCHASE_LAND_AREA | CMD_NO_WATER | CMD_MSG(STR_5806_CAN_T_PURCHASE_THIS_LAND));