diff --git a/src/actions/unit_creator.cpp b/src/actions/unit_creator.cpp
index d4dcc87a0d28..87694cd04b35 100644
--- a/src/actions/unit_creator.cpp
+++ b/src/actions/unit_creator.cpp
@@ -130,7 +130,7 @@ map_location unit_creator::find_location(const config &cfg, const unit* pass_che
 				loc = start_pos_;
 			}
 			if(place == "leader_passable") {
-				deprecated_message("placement=leader_passable", 2, {1, 15, 0}, "Please use placement=leader and passable=yes instead");
+				deprecated_message("placement=leader_passable", DEP_LEVEL::PREEMPTIVE, {1, 15, 0}, "Please use placement=leader and passable=yes instead");
 				pass = true;
 			}
 		}
@@ -144,10 +144,10 @@ map_location unit_creator::find_location(const config &cfg, const unit* pass_che
 				loc = map_location(cfg, resources::gamedata);
 			}
 			if(place == "map_passable") {
-				deprecated_message("placement=map_passable", 2, {1, 15, 0}, "Please use placement=map and passable=yes instead");
+				deprecated_message("placement=map_passable", DEP_LEVEL::PREEMPTIVE, {1, 15, 0}, "Please use placement=map and passable=yes instead");
 				pass = true;
 			} else if(place == "map_overwrite") {
-				deprecated_message("placement=map_overwrite", 2, {1, 15, 0}, "Please use placement=map and overwrite=yes instead");
+				deprecated_message("placement=map_overwrite", DEP_LEVEL::PREEMPTIVE, {1, 15, 0}, "Please use placement=map and overwrite=yes instead");
 				vacant = false;
 			}
 		}
diff --git a/src/ai/lua/core.cpp b/src/ai/lua/core.cpp
index 363d9b682a6a..6d3d7a745741 100644
--- a/src/ai/lua/core.cpp
+++ b/src/ai/lua/core.cpp
@@ -390,7 +390,7 @@ static int cfun_ai_get_targets(lua_State *L)
 // (and the things so deprecated) OR add a version parameter to the macro.
 // Also note that the name MUST be a string literal.
 #define DEPRECATED_ASPECT_MESSAGE(name) \
-	deprecated_message("ai.get_" name, 2, {1, 15, 0}, "Use ai.aspects." name " instead")
+	deprecated_message("ai.get_" name, DEP_LEVEL::PREEMPTIVE, {1, 15, 0}, "Use ai.aspects." name " instead")
 
 // Aspect section
 static int cfun_ai_get_aggression(lua_State *L)
diff --git a/src/config.cpp b/src/config.cpp
index c2f0d6cf9b4d..43cdf050cb1c 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -725,7 +725,7 @@ const config::attribute_value& config::get_old_attribute(
 		if(!in_tag.empty()) {
 			const std::string what = "[" + in_tag + "]" + old_key + "=";
 			const std::string msg = "Use " + key + "= instead.";
-			deprecated_message(what, 1, "", msg);
+			deprecated_message(what, DEP_LEVEL::INDEFINITE, "", msg);
 			lg::wml_error() << msg;
 		}
 
diff --git a/src/deprecation.cpp b/src/deprecation.cpp
index a30f106b0ee4..1ae70f53a3b8 100644
--- a/src/deprecation.cpp
+++ b/src/deprecation.cpp
@@ -28,14 +28,16 @@
 // and so on and so on.
 static lg::log_domain log_deprecate("deprecation", -1);
 
-std::string deprecated_message(const std::string& elem_name, int level, const version_info& version, const std::string& detail) {
+std::string deprecated_message(const std::string& elem_name, DEP_LEVEL level, const version_info& version, const std::string& detail) {
 	utils::string_map msg_params = {{"elem", elem_name}};
 	lg::logger* log_ptr = nullptr;
 	std::string message;
-	if(level == 1) {
+	switch(level) {
+	case DEP_LEVEL::INDEFINITE:
 		log_ptr = &lg::info();
 		message = VGETTEXT("$elem has been deprecated indefinitely.", msg_params);
-	} else if(level == 2) {
+		break;
+	case DEP_LEVEL::PREEMPTIVE:
 		log_ptr = &lg::warn();
 		if(game_config::wesnoth_version < version) {
 			msg_params["version"] = version.str();
@@ -43,15 +45,18 @@ std::string deprecated_message(const std::string& elem_name, int level, const ve
 		} else {
 			message = VGETTEXT("$elem has been deprecated and may be removed at any time.", msg_params);
 		}
-	} else if(level == 3) {
+		break;
+	case DEP_LEVEL::FOR_REMOVAL:
 		log_ptr = &lg::err();
 		msg_params["version"] = version.str();
 		message = VGETTEXT("$elem has been deprecated and will be removed in the next version ($version).", msg_params);
-	} else if(level == 4) {
+		break;
+	case DEP_LEVEL::REMOVED:
 		log_ptr = &lg::err();
 		message = VGETTEXT("$elem has been deprecated and removed.", msg_params);
-	} else {
-		utils::string_map err_params = {{"level", std::to_string(level)}};
+		break;
+	default: // Not impossible, in case level was given an invalid value from a cast.
+		utils::string_map err_params = {{"level", std::to_string(int(level))}};
 		// Note: This message is duplicated in data/lua/core.lua
 		// Any changes should be mirrorred there.
 		std::string msg = VGETTEXT("Invalid deprecation level $level (should be 1-4)", err_params);
diff --git a/src/deprecation.hpp b/src/deprecation.hpp
index a52a7c82cb97..afed12f267bc 100644
--- a/src/deprecation.hpp
+++ b/src/deprecation.hpp
@@ -11,10 +11,14 @@
    See the COPYING file for more details.
 */
 
+#pragma once
+
 #include <string>
 
+enum class DEP_LEVEL {INDEFINITE = 1, PREEMPTIVE, FOR_REMOVAL, REMOVED};
+
 // Note: When using version (for level 2 or 3 deprecation), specify the first version
 // in which the feature could be removed... NOT the version at which it was deprecated.
 // For level 1 or 4 deprecation, it's fine to just pass an empty string, as the parameter will not be used.
 // It returns the final translated deprecation message, in case you want to output it elsewhere as well.
-std::string deprecated_message(const std::string& elem_name, int level, const class version_info& version, const std::string& detail = "");
+std::string deprecated_message(const std::string& elem_name, DEP_LEVEL level, const class version_info& version, const std::string& detail = "");
diff --git a/src/game_events/menu_item.cpp b/src/game_events/menu_item.cpp
index 16747cc1e1b0..00d66c2b7471 100644
--- a/src/game_events/menu_item.cpp
+++ b/src/game_events/menu_item.cpp
@@ -82,7 +82,7 @@ wml_menu_item::wml_menu_item(const std::string& id, const config& cfg)
 	, is_synced_(cfg["synced"].to_bool(true))
 {
 	if(cfg.has_attribute("needs_select")) {
-		deprecated_message("needs_select", 1, {1, 15, 0});
+		deprecated_message("needs_select", DEP_LEVEL::INDEFINITE, {1, 15, 0});
 	}
 	gui2::legacy_menu_item parsed(cfg["description"].str(), "Multiple columns in [set_menu_item] are no longer supported; the image is specified by image=.");
 	if(parsed.contained_markup()) {
@@ -287,7 +287,7 @@ void wml_menu_item::update(const vconfig& vcfg)
 	}
 
 	if(vcfg.has_attribute("needs_select")) {
-		deprecated_message("needs_select", 1, {1, 15, 0});
+		deprecated_message("needs_select", DEP_LEVEL::INDEFINITE, {1, 15, 0});
 		needs_select_ = vcfg["needs_select"].to_bool();
 	}
 
diff --git a/src/gui/auxiliary/old_markup.cpp b/src/gui/auxiliary/old_markup.cpp
index 35ccb64ffbe4..b870456edbc3 100644
--- a/src/gui/auxiliary/old_markup.cpp
+++ b/src/gui/auxiliary/old_markup.cpp
@@ -68,7 +68,7 @@ legacy_menu_item::legacy_menu_item(const std::string& str, const std::string dep
 	}
 
 	if(contained_markup_) {
-		deprecated_message("Legacy DescriptionWML markup (&img=col1=col2)", 3, {1, 15, 0}, deprecation_msg);
+		deprecated_message("Legacy DescriptionWML markup (&img=col1=col2)", DEP_LEVEL::FOR_REMOVAL, {1, 15, 0}, deprecation_msg);
 	}
 }
 }
diff --git a/src/gui/dialogs/campaign_difficulty.cpp b/src/gui/dialogs/campaign_difficulty.cpp
index 511916e36613..b4104a7f1636 100644
--- a/src/gui/dialogs/campaign_difficulty.cpp
+++ b/src/gui/dialogs/campaign_difficulty.cpp
@@ -82,9 +82,9 @@ config generate_difficulty_config(const config& source)
 
 	// Convert legacy format to new-style config if latter not present
 	if(result.empty() && source.has_attribute("difficulties")) {
-		deprecated_message("[campaign]difficulties", 3, {1, 15, 0}, "Use [difficulty] instead.");
+		deprecated_message("[campaign]difficulties", DEP_LEVEL::FOR_REMOVAL, {1, 15, 0}, "Use [difficulty] instead.");
 		if(source.has_attribute("difficulty_descriptions")) {
-			deprecated_message("[campaign]difficulty_descriptions", 3, {1, 15, 0}, "Use [difficulty] instead.");
+			deprecated_message("[campaign]difficulty_descriptions", DEP_LEVEL::FOR_REMOVAL, {1, 15, 0}, "Use [difficulty] instead.");
 		}
 
 		std::vector<std::string> difficulty_list = utils::split(source["difficulties"]);
diff --git a/src/gui/dialogs/multiplayer/mp_options_helper.cpp b/src/gui/dialogs/multiplayer/mp_options_helper.cpp
index f443fee38891..24e1c631e40f 100644
--- a/src/gui/dialogs/multiplayer/mp_options_helper.cpp
+++ b/src/gui/dialogs/multiplayer/mp_options_helper.cpp
@@ -260,7 +260,7 @@ void mp_options_helper::display_custom_options(const std::string& type, int node
 
 			} else if(opt.key == "choice" || opt.key == "combo") {
 				if(opt.key == "combo") {
-					deprecated_message("combo", 3, {1, 15, 0}, "Use [choice] instead.");
+					deprecated_message("combo", DEP_LEVEL::FOR_REMOVAL, {1, 15, 0}, "Use [choice] instead.");
 				}
 
 				if(!option_cfg.has_child("item")) {
diff --git a/src/scripting/game_lua_kernel.cpp b/src/scripting/game_lua_kernel.cpp
index 56674692190b..8a6b88f5c051 100644
--- a/src/scripting/game_lua_kernel.cpp
+++ b/src/scripting/game_lua_kernel.cpp
@@ -850,7 +850,7 @@ int game_lua_kernel::intf_set_end_campaign_text(lua_State *L)
 
 int game_lua_kernel::intf_set_next_scenario(lua_State *L)
 {
-	deprecated_message("wesnoth.set_next_scenario", 1, "");
+	deprecated_message("wesnoth.set_next_scenario", DEP_LEVEL::INDEFINITE, "");
 	gamedata().set_next_scenario(luaL_checkstring(L, 1));
 	return 0;
 }
@@ -2091,7 +2091,7 @@ int game_lua_kernel::intf_put_unit(lua_State *L)
 			if (!map().on_board(loc))
 				return luaL_argerror(L, 1, "invalid location");
 		} else if (unit_arg != 1) {
-			deprecated_message("wesnoth.put_unit(x, y, unit)", 3, {1, 15, 0}, "Use wesnoth.put_unit(unit, x, y) or unit:to_map(x, y) instead.");
+			deprecated_message("wesnoth.put_unit(x, y, unit)", DEP_LEVEL::FOR_REMOVAL, {1, 15, 0}, "Use wesnoth.put_unit(unit, x, y) or unit:to_map(x, y) instead.");
 		}
 		put_unit_helper(loc);
 		u.put_map(loc);
@@ -2105,14 +2105,14 @@ int game_lua_kernel::intf_put_unit(lua_State *L)
 			if (!map().on_board(loc))
 				return luaL_argerror(L, 2, "invalid location");
 		} else if (unit_arg != 1) {
-			deprecated_message("wesnoth.put_unit(x, y, unit)", 3, {1, 15, 0}, "Use wesnoth.put_unit(unit, x, y) or unit:to_map(x, y) instead.");
+			deprecated_message("wesnoth.put_unit(x, y, unit)", DEP_LEVEL::FOR_REMOVAL, {1, 15, 0}, "Use wesnoth.put_unit(unit, x, y) or unit:to_map(x, y) instead.");
 		}
 		unit_ptr u(new unit(cfg, true, vcfg));
 		put_unit_helper(loc);
 		u->set_location(loc);
 		units().insert(u);
 	} else {
-		deprecated_message("wesnoth.put_unit(x, y)", 3, {1, 15, 0}, "Use wesnoth.erase_unit(x, y) or unit:erase() instead.");
+		deprecated_message("wesnoth.put_unit(x, y)", DEP_LEVEL::FOR_REMOVAL, {1, 15, 0}, "Use wesnoth.erase_unit(x, y) or unit:erase() instead.");
 		put_unit_helper(loc);
 		return 0; // Don't fire event when unit is only erase
 	}
@@ -2556,7 +2556,7 @@ int game_lua_kernel::intf_simulate_combat(lua_State *L)
  */
 static int intf_set_music(lua_State *L)
 {
-	deprecated_message("wesnoth.set_music", 1, "", "Use the wesnoth.playlist table instead!");
+	deprecated_message("wesnoth.set_music", DEP_LEVEL::INDEFINITE, "", "Use the wesnoth.playlist table instead!");
 	if (lua_isnoneornil(L, 1)) {
 		sound::commit_music_changes();
 		return 0;
@@ -2629,7 +2629,7 @@ int game_lua_kernel::intf_scroll_to_tile(lua_State *L)
 int game_lua_kernel::intf_select_hex(lua_State *L)
 {
 	events::command_disabler command_disabler;
-	deprecated_message("wesnoth.select_hex", 2, {1, 15, 0}, "Use wesnoth.select_unit and/or wesnoth.highlight_hex instead.");
+	deprecated_message("wesnoth.select_hex", DEP_LEVEL::PREEMPTIVE, {1, 15, 0}, "Use wesnoth.select_unit and/or wesnoth.highlight_hex instead.");
 
 	// Need this because check_location may change the stack
 	// By doing this now, we ensure that it won't do so when
@@ -3124,7 +3124,7 @@ static int intf_add_modification(lua_State *L)
 	std::string sm = m;
 	if (sm == "advance") { // Maintain backwards compatibility
 		sm = "advancement";
-		deprecated_message("\"advance\" modification type", 2, {1, 15, 0}, "Use \"advancement\" instead.");
+		deprecated_message("\"advance\" modification type", DEP_LEVEL::PREEMPTIVE, {1, 15, 0}, "Use \"advancement\" instead.");
 	}
 	if (sm != "advancement" && sm != "object" && sm != "trait") {
 		return luaL_argerror(L, 2, "unknown modification type");
@@ -3380,7 +3380,7 @@ static int intf_modify_ai_old(lua_State *L)
 	config cfg;
 	luaW_toconfig(L, 1, cfg);
 	int side = cfg["side"];
-	deprecated_message("wesnoth.modify_ai", 2, {1, 15, 0}, "Use wesnoth.add_ai_component, wesnoth.delete_ai_component, or wesnoth.change_ai_component.");
+	deprecated_message("wesnoth.modify_ai", DEP_LEVEL::PREEMPTIVE, {1, 15, 0}, "Use wesnoth.add_ai_component, wesnoth.delete_ai_component, or wesnoth.change_ai_component.");
 	ai::manager::get_singleton().modify_active_ai_for_side(side, cfg);
 	return 0;
 }
diff --git a/src/scripting/lua_kernel_base.cpp b/src/scripting/lua_kernel_base.cpp
index e095389546c6..7898f81a88d9 100644
--- a/src/scripting/lua_kernel_base.cpp
+++ b/src/scripting/lua_kernel_base.cpp
@@ -284,12 +284,13 @@ static int intf_log(lua_State *L) {
  */
 static int intf_deprecated_message(lua_State* L) {
 	const std::string elem = luaL_checkstring(L, 1);
-	const int level = luaL_checkinteger(L, 2);
+	// This could produce an invalid deprecation level, but that possibility is handled in deprecated_message()
+	const DEP_LEVEL level = DEP_LEVEL(luaL_checkinteger(L, 2));
 	const std::string ver_str = lua_isnoneornil(L, 3) ? "" : luaL_checkstring(L, 3);
 	const std::string detail = luaW_checktstring(L, 4);
 	const version_info ver = ver_str.empty() ? game_config::version : ver_str;
 	const std::string msg = deprecated_message(elem, level, ver, detail);
-	if(level < 1 || level >= 4) {
+	if(level < DEP_LEVEL::INDEFINITE || level >= DEP_LEVEL::REMOVED) {
 		// Invalid deprecation level or level 4 deprecation should raise an interpreter error
 		lua_push(L, msg);
 		return lua_error(L);
diff --git a/src/serialization/preprocessor.cpp b/src/serialization/preprocessor.cpp
index 344d73649ae2..8c282bc184aa 100644
--- a/src/serialization/preprocessor.cpp
+++ b/src/serialization/preprocessor.cpp
@@ -1154,7 +1154,7 @@ bool preprocessor_data::get_chunk()
 			std::string symbol = items.front();
 			items.erase(items.begin());
 			int found_arg = 0, found_enddef = 0, found_deprecate = 0;
-			int deprecation_level = -1;
+			boost::optional<DEP_LEVEL> deprecation_level;
 			std::string buffer, deprecation_detail;
 			version_info deprecation_version = game_config::wesnoth_version;
 			for(;;) {
@@ -1217,12 +1217,18 @@ bool preprocessor_data::get_chunk()
 							buffer.erase(buffer.end() - 11, buffer.end());
 							skip_spaces();
 							try {
-								deprecation_level = std::max(deprecation_level, std::stoi(read_word()));
+								DEP_LEVEL level = DEP_LEVEL(std::stoi(read_word()));
+								if(deprecation_level) {
+									deprecation_level = std::max(*deprecation_level, level);
+								} else {
+									deprecation_level = level;
+								}
 							} catch(std::invalid_argument&) {
-								deprecation_level = 0;
+								// Meh, fall back to default of PREEMPTIVE...
+								deprecation_level = DEP_LEVEL::PREEMPTIVE;
 							}
 							deprecation_version = game_config::wesnoth_version;
-							if(deprecation_level == 2 || deprecation_level == 3) {
+							if(deprecation_level == DEP_LEVEL::PREEMPTIVE || deprecation_level == DEP_LEVEL::FOR_REMOVAL) {
 								skip_spaces();
 								deprecation_version = std::max(deprecation_version, version_info(read_word()));
 							}
@@ -1272,7 +1278,7 @@ bool preprocessor_data::get_chunk()
 				buffer.erase(buffer.end() - 7, buffer.end());
 				(*parent_.defines_)[symbol]
 						= preproc_define(buffer, items, optargs, parent_.textdomain_, linenum, parent_.location_,
-						deprecation_detail, deprecation_level, deprecation_version);
+						deprecation_detail, *deprecation_level, deprecation_version);
 
 				LOG_PREPROC << "defining macro " << symbol << " (location " << get_location(parent_.location_) << ")\n";
 			}
@@ -1397,12 +1403,14 @@ bool preprocessor_data::get_chunk()
 		} else if(command == "deprecated") {
 			// The current file is deprecated, so print a message
 			skip_spaces();
-			int level = 0;
+			DEP_LEVEL level = DEP_LEVEL::PREEMPTIVE;
 			try {
-				level = std::stoi(read_word());
-			} catch(std::invalid_argument&) {}
+				level = DEP_LEVEL(std::stoi(read_word()));
+			} catch(std::invalid_argument&) {
+				// Meh, just fall back to the default of PREEMPTIVE...
+			}
 			version_info version = game_config::wesnoth_version;
-			if(level == 2 || level == 3) {
+			if(level == DEP_LEVEL::PREEMPTIVE || level == DEP_LEVEL::FOR_REMOVAL) {
 				skip_spaces();
 				version = version_info(read_word());
 			}
@@ -1488,7 +1496,7 @@ bool preprocessor_data::get_chunk()
 				const std::string& dir = filesystem::directory_name(val.location.substr(0, val.location.find(' ')));
 
 				if(val.is_deprecated()) {
-					deprecated_message(symbol, val.deprecation_level, val.deprecation_version, val.deprecation_message);
+					deprecated_message(symbol, *val.deprecation_level, val.deprecation_version, val.deprecation_message);
 				}
 
 				for(size_t i = 0; i < nb_arg; ++i) {
diff --git a/src/serialization/preprocessor.hpp b/src/serialization/preprocessor.hpp
index 9ae8c96780d0..35baee8234af 100644
--- a/src/serialization/preprocessor.hpp
+++ b/src/serialization/preprocessor.hpp
@@ -21,9 +21,11 @@
 #include <iosfwd>
 #include <map>
 #include <vector>
+#include <boost/optional.hpp>
 
 #include "exceptions.hpp"
 #include "version.hpp"
+#include "deprecation.hpp"
 
 class config_writer;
 class config;
@@ -59,7 +61,7 @@ struct preproc_define
 			int line,
 			const std::string& loc,
 			const std::string& dep_msg,
-			int dep_lvl, const version_info& dep_ver)
+			DEP_LEVEL dep_lvl, const version_info& dep_ver)
 		: value(val)
 		, arguments(args)
 		, optional_arguments(optargs)
@@ -86,12 +88,12 @@ struct preproc_define
 
 	std::string deprecation_message;
 
-	int deprecation_level = -1;
+	boost::optional<DEP_LEVEL> deprecation_level;
 
 	version_info deprecation_version;
 
 	bool is_deprecated() const {
-		return deprecation_level > 0;
+		return deprecation_level != boost::none;
 	}
 
 	void write(config_writer&, const std::string&) const;
diff --git a/src/storyscreen/parser.cpp b/src/storyscreen/parser.cpp
index c0e7936f1c33..f7937496de93 100644
--- a/src/storyscreen/parser.cpp
+++ b/src/storyscreen/parser.cpp
@@ -105,7 +105,8 @@ void story_parser::resolve_wml(const vconfig& cfg)
 		// [deprecated_message]
 		else if(key == "deprecated_message") {
 			// Won't appear until the scenario start event finishes.
-			deprecated_message(node["what"], node["level"], node["version"].str(), node["message"]);
+			DEP_LEVEL level = DEP_LEVEL(node["level"].to_int(2));
+			deprecated_message(node["what"], level, node["version"].str(), node["message"]);
 		}
 		// [wml_message]
 		else if(key == "wml_message") {
diff --git a/src/units/abilities.cpp b/src/units/abilities.cpp
index 05f47638dfba..886b4881b26a 100644
--- a/src/units/abilities.cpp
+++ b/src/units/abilities.cpp
@@ -1055,7 +1055,7 @@ effect::effect(const unit_ability_list& list, int def, bool backstab) :
 		const std::string& effect_id = cfg[cfg["id"].empty() ? "name" : "id"];
 
 		if (!cfg["backstab"].blank()) {
-			deprecated_message("backstab= in weapon specials", 2, {1, 15, 0}, "Use [filter_adjacent] instead.");
+			deprecated_message("backstab= in weapon specials", DEP_LEVEL::PREEMPTIVE, {1, 15, 0}, "Use [filter_adjacent] instead.");
 		}
 
 		if (!backstab && cfg["backstab"].to_bool())
diff --git a/src/units/unit.cpp b/src/units/unit.cpp
index 74a8ed80d12d..74e297b3202d 100644
--- a/src/units/unit.cpp
+++ b/src/units/unit.cpp
@@ -2344,7 +2344,7 @@ void unit::apply_modifications()
 
 	for(const auto& mod : ModificationTypes) {
 		if(mod == "advance" && modifications_.has_child(mod)) {
-			deprecated_message("[advance]", 2, {1, 15, 0}, "Use [advancement] instead.");
+			deprecated_message("[advance]", DEP_LEVEL::PREEMPTIVE, {1, 15, 0}, "Use [advancement] instead.");
 		}
 
 		for(const config& m : modifications_.child_range(mod)) {