diff --git a/src/fios_gui.cpp b/src/fios_gui.cpp
--- a/src/fios_gui.cpp
+++ b/src/fios_gui.cpp
@@ -229,7 +229,7 @@ struct SaveLoadWindow : public Window {
 private:
 	QueryString filename_editbox; ///< Filename editbox.
 	AbstractFileType abstract_filetype; /// Type of file to select.
-	FileOperation fop;            ///< File operation to perform.
+	SaveLoadOperation fop;        ///< File operation to perform.
 	FileList fios_items;          ///< Save game list.
 	FiosItem o_dir;
 	const FiosItem *selected;     ///< Selected game in #fios_items, or \c NULL.
@@ -243,13 +243,13 @@ public:
 		this->filename_editbox.text.UpdateSize();
 	}
 
-	SaveLoadWindow(WindowDesc *desc, AbstractFileType abstract_filetype, FileOperation fop)
+	SaveLoadWindow(WindowDesc *desc, AbstractFileType abstract_filetype, SaveLoadOperation fop)
 			: Window(desc), filename_editbox(64), abstract_filetype(abstract_filetype), fop(fop)
 	{
-		assert(this->fop == FOP_SAVE || this->fop == FOP_LOAD);
+		assert(this->fop == SLO_SAVE || this->fop == SLO_LOAD);
 
 		/* For saving, construct an initial file name. */
-		if (this->fop == FOP_SAVE) {
+		if (this->fop == SLO_SAVE) {
 			switch (this->abstract_filetype) {
 				case FT_SAVEGAME:
 					this->GenerateFileName();
@@ -268,7 +268,7 @@ public:
 		this->filename_editbox.ok_button = WID_SL_SAVE_GAME;
 
 		this->CreateNestedTree(true);
-		if (this->fop == FOP_LOAD && this->abstract_filetype == FT_SAVEGAME) {
+		if (this->fop == SLO_LOAD && this->abstract_filetype == FT_SAVEGAME) {
 			this->GetWidget<NWidgetStacked>(WID_SL_CONTENT_DOWNLOAD_SEL)->SetDisplayedPlane(SZSP_HORIZONTAL);
 		}
 
@@ -276,15 +276,15 @@ public:
 		StringID caption_string;
 		switch (this->abstract_filetype) {
 			case FT_SAVEGAME:
-				caption_string = (this->fop == FOP_SAVE) ? STR_SAVELOAD_SAVE_CAPTION : STR_SAVELOAD_LOAD_CAPTION;
+				caption_string = (this->fop == SLO_SAVE) ? STR_SAVELOAD_SAVE_CAPTION : STR_SAVELOAD_LOAD_CAPTION;
 				break;
 
 			case FT_SCENARIO:
-				caption_string = (this->fop == FOP_SAVE) ? STR_SAVELOAD_SAVE_SCENARIO : STR_SAVELOAD_LOAD_SCENARIO;
+				caption_string = (this->fop == SLO_SAVE) ? STR_SAVELOAD_SAVE_SCENARIO : STR_SAVELOAD_LOAD_SCENARIO;
 				break;
 
 			case FT_HEIGHTMAP:
-				caption_string = (this->fop == FOP_SAVE) ? STR_SAVELOAD_SAVE_HEIGHTMAP : STR_SAVELOAD_LOAD_HEIGHTMAP;
+				caption_string = (this->fop == SLO_SAVE) ? STR_SAVELOAD_SAVE_HEIGHTMAP : STR_SAVELOAD_LOAD_HEIGHTMAP;
 				break;
 
 			default:
@@ -328,7 +328,7 @@ public:
 		}
 
 		/* Focus the edit box by default in the save windows */
-		if (this->fop == FOP_SAVE) this->SetFocusedWidget(WID_SL_SAVE_OSK_TITLE);
+		if (this->fop == SLO_SAVE) this->SetFocusedWidget(WID_SL_SAVE_OSK_TITLE);
 	}
 
 	virtual ~SaveLoadWindow()
@@ -438,7 +438,7 @@ public:
 					}
 
 					/* Hide the NewGRF stuff when saving. We also hide the button. */
-					if (this->fop == FOP_LOAD && (this->abstract_filetype == FT_SAVEGAME || this->abstract_filetype == FT_SCENARIO)) {
+					if (this->fop == SLO_LOAD && (this->abstract_filetype == FT_SAVEGAME || this->abstract_filetype == FT_SCENARIO)) {
 						y += WD_PAR_VSEP_NORMAL;
 						if (y > y_max) break;
 
@@ -583,19 +583,19 @@ public:
 
 							if (GetDetailedFileType(file->type) == DFT_GAME_FILE) {
 								/* Other detailed file types cannot be checked before. */
-								SaveOrLoad(name, FOP_CHECK, DFT_GAME_FILE, NO_DIRECTORY, false);
+								SaveOrLoad(name, SLO_CHECK, DFT_GAME_FILE, NO_DIRECTORY, false);
 							}
 
 							this->InvalidateData(1);
 						}
-						if (this->fop == FOP_SAVE) {
+						if (this->fop == SLO_SAVE) {
 							/* Copy clicked name to editbox */
 							this->filename_editbox.text.Assign(file->title);
 							this->SetWidgetDirty(WID_SL_SAVE_OSK_TITLE);
 						}
 					} else if (!_load_check_data.HasErrors()) {
 						this->selected = file;
-						if (this->fop == FOP_LOAD) {
+						if (this->fop == SLO_LOAD) {
 							if (this->abstract_filetype == FT_SAVEGAME || this->abstract_filetype == FT_SCENARIO) {
 								this->OnClick(pt, WID_SL_LOAD_BUTTON, 1);
 							} else {
@@ -621,7 +621,7 @@ public:
 					ShowErrorMessage(STR_NETWORK_ERROR_NOTAVAILABLE, INVALID_STRING_ID, WL_ERROR);
 				} else {
 #if defined(ENABLE_NETWORK)
-					assert(this->fop == FOP_LOAD);
+					assert(this->fop == SLO_LOAD);
 					switch (this->abstract_filetype) {
 						default: NOT_REACHED();
 						case FT_SCENARIO:  ShowNetworkContentListWindow(NULL, CONTENT_TYPE_SCENARIO);  break;
@@ -654,7 +654,7 @@ public:
 	virtual void OnTimeout()
 	{
 		/* Widgets WID_SL_DELETE_SELECTION and WID_SL_SAVE_GAME only exist when saving to a file. */
-		if (this->fop != FOP_SAVE) return;
+		if (this->fop != SLO_SAVE) return;
 
 		if (this->IsWidgetLowered(WID_SL_DELETE_SELECTION)) { // Delete button clicked
 			if (!FiosDelete(this->filename_editbox.text.buf)) {
@@ -707,7 +707,7 @@ public:
 				/* Selection changes */
 				if (!gui_scope) break;
 
-				if (this->fop != FOP_LOAD) break;
+				if (this->fop != SLO_LOAD) break;
 
 				switch (this->abstract_filetype) {
 					case FT_HEIGHTMAP:
@@ -764,12 +764,12 @@ static WindowDesc _save_dialog_desc(
  * @param abstract_filetype Kind of file to handle.
  * @param fop File operation to perform (load or save).
  */
-void ShowSaveLoadDialog(AbstractFileType abstract_filetype, FileOperation fop)
+void ShowSaveLoadDialog(AbstractFileType abstract_filetype, SaveLoadOperation fop)
 {
 	DeleteWindowById(WC_SAVELOAD, 0);
 
 	WindowDesc *sld;
-	if (fop == FOP_SAVE) {
+	if (fop == SLO_SAVE) {
 		sld = &_save_dialog_desc;
 	} else {
 		/* Dialogue for loading a file. */