diff --git a/src/lang/english.txt b/src/lang/english.txt
index b1c50d6857..592d5830b4 100644
--- a/src/lang/english.txt
+++ b/src/lang/english.txt
@@ -5972,3 +5972,5 @@ CM_STR_NETWORK_SERVER_LIST_FILTER_REDDIT                                       :
 CM_STR_NETWORK_SERVER_LIST_FILTER_TEAMGAME                                     :{BLACK}TeamGame
 CM_STR_NETWORK_SERVER_LIST_FILTER_TOOLTIP                                      :{BLACK}Filter this community
 
+CM_STR_CONFIG_SETTING_ENABLE_POLYRAIL_TERRAFORM :Enable experimental auto-terraforming with polyrail
+CM_STR_CONFIG_SETTING_ENABLE_POLYRAIL_TERRAFORM_HELPTEXT :Allows to use experimental auto-terraforming mode with polyrail tool (by pressing Fn modifier).
\ No newline at end of file
diff --git a/src/rail_gui.cpp b/src/rail_gui.cpp
index 039ca48057..2f98c65e51 100644
--- a/src/rail_gui.cpp
+++ b/src/rail_gui.cpp
@@ -1080,7 +1080,7 @@ struct BuildRailToolbarWindow : Window {
 
 	EventState CM_OnFnModStateChange() override
 	{
-		if (this->IsWidgetLowered(WID_RAT_POLYRAIL)) {
+		if (_settings_client.gui.cm_enable_polyrail_terraform && this->IsWidgetLowered(WID_RAT_POLYRAIL)) {
 			return ES_HANDLED;
 		}
 		return ES_NOT_HANDLED;
diff --git a/src/settings_gui.cpp b/src/settings_gui.cpp
index 1973f32f50..62590c7544 100644
--- a/src/settings_gui.cpp
+++ b/src/settings_gui.cpp
@@ -1655,6 +1655,7 @@ static SettingsContainer &GetSettingsTree()
 				construction->Add(new SettingEntry("gui.quick_goto"));
 				construction->Add(new SettingEntry("gui.default_rail_type"));
 				construction->Add(new SettingEntry("gui.cm_use_improved_station_join"));
+				construction->Add(new SettingEntry("gui.cm_enable_polyrail_terraform"));
 			}
 
 			interface->Add(new SettingEntry("gui.fast_forward_speed_limit"));
diff --git a/src/settings_type.h b/src/settings_type.h
index ae5c77d3c7..0552d4db3e 100644
--- a/src/settings_type.h
+++ b/src/settings_type.h
@@ -223,7 +223,7 @@ struct GUISettings {
 	bool cm_show_apm;
 	uint8 cm_graph_background;
 	bool cm_show_client_overlay;
-
+	bool cm_enable_polyrail_terraform;
 	/**
 	 * Returns true when the user has sufficient privileges to edit newgrfs on a running game
 	 * @return whether the user has sufficient privileges to edit newgrfs in an existing game
diff --git a/src/table/settings/cmclient_settings.ini b/src/table/settings/cmclient_settings.ini
index e04ef2d22e..b925ad73ad 100644
--- a/src/table/settings/cmclient_settings.ini
+++ b/src/table/settings/cmclient_settings.ini
@@ -262,3 +262,10 @@ var      = gui.cm_show_client_overlay
 def      = false
 cat      = SC_BASIC
 flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC
+
+[SDTC_BOOL]
+var      = gui.cm_enable_polyrail_terraform
+def      = false
+str      = CM_STR_CONFIG_SETTING_ENABLE_POLYRAIL_TERRAFORM
+strhelp  = CM_STR_CONFIG_SETTING_ENABLE_POLYRAIL_TERRAFORM_HELPTEXT
+cat      = SC_EXPERT
diff --git a/src/viewport.cpp b/src/viewport.cpp
index a326ae3de2..1bfbc16bc4 100644
--- a/src/viewport.cpp
+++ b/src/viewport.cpp
@@ -2695,7 +2695,7 @@ void UpdateTileSelection()
 								_thd.new_size.y = y2 - y1 + TILE_SIZE;
 							}
 						}
-						_thd.cm_new_poly_terra = citymania::_fn_mod;
+						_thd.cm_new_poly_terra = _settings_client.gui.cm_enable_polyrail_terraform && citymania::_fn_mod;
 						break;
 					}
 					/* HT_RAIL */