diff --git a/src/rail_gui.h b/src/rail_gui.h
--- a/src/rail_gui.h
+++ b/src/rail_gui.h
@@ -15,7 +15,7 @@
 
 struct Window *ShowBuildRailToolbar(RailType railtype);
 void ReinitGuiAfterToggleElrail(bool disable);
-bool ResetSignalVariant(int32 = 0);
+void ResetSignalVariant(int32 = 0);
 void InitializeRailGUI();
 DropDownList GetRailTypeDropDownList(bool for_replacement = false, bool all_option = false);