diff --git a/data/gui/default/widget/label_default.cfg b/data/gui/default/widget/label_default.cfg
index 535a530a37f4..ac68e0300f75 100644
--- a/data/gui/default/widget/label_default.cfg
+++ b/data/gui/default/widget/label_default.cfg
@@ -96,6 +96,7 @@
 #enddef
 
 {_GUI_DEFINITION "default"       "default label"            DEFAULT      ()     DEFAULT ({GUI__TEXT_VERTICALLY_CENTRED})}
+{_GUI_DEFINITION "default_bold"  "default label, bold font" DEFAULT      "bold" DEFAULT ({GUI__TEXT_VERTICALLY_CENTRED})}
 {_GUI_DEFINITION "scroll_label"  "scroll label"             DEFAULT      ()     DEFAULT 0}
 {_GUI_DEFINITION "title"         "label used for titles"    TITLE        "bold" TITLE   ({GUI__TEXT_VERTICALLY_CENTRED})}
 {_GUI_DEFINITION "default_large" "default, large font size" LARGE        ()     DEFAULT ({GUI__TEXT_VERTICALLY_CENTRED})}
diff --git a/data/gui/default/window/wml_error.cfg b/data/gui/default/window/wml_error.cfg
new file mode 100644
index 000000000000..1e851242d46c
--- /dev/null
+++ b/data/gui/default/window/wml_error.cfg
@@ -0,0 +1,173 @@
+#textdomain wesnoth-lib
+###
+### Dialog used to report WML parser or preprocessor errors.
+###
+
+[window]
+	id = "wml_error"
+	description = "WML preprocessor/parser error report dialog."
+
+	[resolution]
+		definition = "default"
+
+		#click_dismiss = "true"
+		maximum_width = 600
+		maximum_height = 600
+
+		automatic_placement = "true"
+		vertical_placement = "center"
+		horizontal_placement = "center"
+
+		[tooltip]
+			id = "tooltip_large"
+		[/tooltip]
+
+		[helptip]
+			id = "tooltip_large"
+		[/helptip]
+
+		[grid]
+
+			[row]
+
+				[column]
+					border = "all"
+					border_size = 5
+					horizontal_alignment = "left"
+
+					[label]
+						definition = "title"
+						label = _ "Error"
+					[/label]
+				[/column]
+
+			[/row]
+
+			[row]
+
+				[column]
+					border = "all"
+					border_size = 5
+					horizontal_alignment = "left"
+
+					[label]
+						id = "summary"
+						definition = "default"
+						wrap = true
+					[/label]
+				[/column]
+
+			[/row]
+
+			[row]
+
+				[column]
+					border = "all"
+					border_size = 5
+					horizontal_alignment = "left"
+
+					[label]
+						id = "files"
+						definition = "default"
+						wrap = true
+					[/label]
+				[/column]
+
+			[/row]
+
+			[row]
+
+				[column]
+					border = "all"
+					border_size = 5
+					horizontal_alignment = "left"
+
+					[label]
+						id = "post_summary"
+						definition = "default"
+						wrap = true
+					[/label]
+				[/column]
+
+			[/row]
+
+			[row]
+
+				[column]
+					horizontal_grow = "true"
+
+					[grid]
+
+						[row]
+
+							[column]
+								border = "all"
+								border_size = 5
+								horizontal_alignment = "left"
+								vertical_alignment = "bottom"
+
+								[label]
+									id = "details_heading"
+									definition = "default_bold"
+									label = _ "Details:"
+								[/label]
+							[/column]
+
+							[column]
+								border = "top,left,right"
+								border_size = 5
+								horizontal_alignment = "right"
+
+								[button]
+									id = "copy"
+									definition = "action_copy"
+									label = _ "clipboard^Copy"
+									tooltip = _ "Copy this report to clipboard"
+								[/button]
+							[/column]
+
+						[/row]
+
+					[/grid]
+
+				[/column]
+
+			[/row]
+
+			[row]
+
+				[column]
+					border = "all"
+					border_size = 5
+					horizontal_grow = "true"
+
+					[scroll_label]
+						id = "details"
+						definition = "description"
+					[/scroll_label]
+				[/column]
+
+			[/row]
+
+			[row]
+
+				[column]
+					border = "all"
+					border_size = 5
+					horizontal_alignment = "right"
+
+					[button]
+						id = "ok"
+						definition = "default"
+						label = _ "OK"
+					[/button]
+
+				[/column]
+
+			[/row]
+
+		[/grid]
+
+	[/resolution]
+
+[/window]
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index c486318c6073..23bee82308bb 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -769,6 +769,7 @@ set(wesnoth-main_SRC
 	gui/dialogs/transient_message.cpp
 	gui/dialogs/unit_attack.cpp
 	gui/dialogs/unit_create.cpp
+	gui/dialogs/wml_error.cpp
 	gui/dialogs/wml_message.cpp
 	halo.cpp
 	help.cpp
diff --git a/src/SConscript b/src/SConscript
index 07706414d141..75d943dd573f 100644
--- a/src/SConscript
+++ b/src/SConscript
@@ -395,6 +395,7 @@ wesnoth_sources = Split("""
     gui/dialogs/transient_message.cpp
     gui/dialogs/unit_attack.cpp
     gui/dialogs/unit_create.cpp
+    gui/dialogs/wml_error.cpp
     gui/dialogs/wml_message.cpp
     gui/lib/types/point.cpp
     gui/widgets/button.cpp
diff --git a/src/game.cpp b/src/game.cpp
index 7f944847eaf4..94f81a3ab715 100644
--- a/src/game.cpp
+++ b/src/game.cpp
@@ -466,6 +466,10 @@ static int do_gameloop(int argc, char** argv)
 	const cursor::manager cursor_manager;
 	cursor::set(cursor::WAIT);
 
+#if (defined(_X11) && !defined(__APPLE__)) || defined(_WIN32)
+	SDL_EventState(SDL_SYSWMEVENT, SDL_ENABLE);
+#endif
+
 	loadscreen::global_loadscreen_manager loadscreen_manager(game->disp().video());
 
 	loadscreen::start_stage("init gui");
@@ -492,10 +496,6 @@ static int do_gameloop(int argc, char** argv)
 	loadscreen::start_stage("refresh addons");
 	refresh_addon_version_info_cache();
 
-#if (defined(_X11) && !defined(__APPLE__)) || defined(_WIN32)
-	SDL_EventState(SDL_SYSWMEVENT, SDL_ENABLE);
-#endif
-
 	config tips_of_day;
 
 	loadscreen::start_stage("titlescreen");
diff --git a/src/game_config_manager.cpp b/src/game_config_manager.cpp
index af4f9aab2451..4daebd8b8af7 100644
--- a/src/game_config_manager.cpp
+++ b/src/game_config_manager.cpp
@@ -20,13 +20,14 @@
 #include "cursor.hpp"
 #include "game_config.hpp"
 #include "gettext.hpp"
-#include "gui/dialogs/message.hpp"
+#include "gui/dialogs/wml_error.hpp"
 #include "language.hpp"
 #include "loadscreen.hpp"
 #include "log.hpp"
 #include "resources.hpp"
 #include "scripting/lua.hpp"
 #include "hotkey/hotkey_item.hpp"
+#include "hotkey/hotkey_command.hpp"
 
 #include <boost/foreach.hpp>
 
@@ -174,10 +175,10 @@ void game_config_manager::load_game_config(FORCE_RELOAD_CONFIG force_reload,
 		::init_strings(game_config());
 		theme::set_known_themes(&game_config());
 	} catch(game::error& e) {
-		ERR_CONFIG << "Error loading game configuration files\n";
-		gui2::show_error_message(disp_.video(),
-			_("Error loading game configuration files: '") +
-			e.message + _("' (The game will now exit)"));
+		ERR_CONFIG << "Error loading game configuration files\n" << e.message << '\n';
+		gui2::twml_error::display(
+			_("Error loading game configuration files. The game will now exit."),
+			e.message, disp_.video());
 		throw;
 	}
 
@@ -198,7 +199,8 @@ void game_config_manager::load_addons_cfg()
 
 	get_files_in_dir(user_campaign_dir, &user_files, &user_dirs,
 		ENTIRE_FILE_PATH);
-	std::stringstream user_error_log;
+
+	std::vector<std::string> error_log;
 
 	// Append the $user_campaign_dir/*.cfg files to addons_to_load.
 	BOOST_FOREACH(const std::string& uc, user_files) {
@@ -229,11 +231,11 @@ void game_config_manager::load_addons_cfg()
 				ERR_CONFIG << "error reading usermade add-on '"
 					<< file << "'\n";
 				error_addons.push_back(file);
-				user_error_log << "The format '~" << file.substr(userdata_loc)
-					<< "' is only for single-file add-ons, use '~"
-					<< file.substr(userdata_loc,
+				error_log.push_back("The format '~" + file.substr(userdata_loc)
+					+ "' is only for single-file add-ons, use '~"
+					+ file.substr(userdata_loc,
 						size_minus_extension - userdata_loc)
-					<< "/_main.cfg' instead.\n";
+					+ "/_main.cfg' instead.");
 			}
 			else {
 				addons_to_load.push_back(file);
@@ -258,29 +260,34 @@ void game_config_manager::load_addons_cfg()
 			game_config_.append(umc_cfg);
 		} catch(config::error& err) {
 			ERR_CONFIG << "error reading usermade add-on '" << uc << "'\n";
+			ERR_CONFIG << err.message << '\n';
 			error_addons.push_back(uc);
-			user_error_log << err.message << "\n";
+			error_log.push_back(err.message);
 		} catch(preproc_config::error& err) {
 			ERR_CONFIG << "error reading usermade add-on '" << uc << "'\n";
+			ERR_CONFIG << err.message << '\n';
 			error_addons.push_back(uc);
-			user_error_log << err.message << "\n";
+			error_log.push_back(err.message);
 		} catch(io_exception&) {
 			ERR_CONFIG << "error reading usermade add-on '" << uc << "'\n";
 			error_addons.push_back(uc);
 		}
 	}
 	if(error_addons.empty() == false) {
-		std::stringstream msg;
-		msg << _n("The following add-on had errors and could not be loaded:",
-			"The following add-ons had errors and could not be loaded:",
-				error_addons.size());
-		BOOST_FOREACH(const std::string& error_addon, error_addons) {
-			msg << "\n" << error_addon;
-		}
-
-		msg << '\n' << _("ERROR DETAILS:") << '\n' << user_error_log.str();
-
-		gui2::show_error_message(disp_.video(),msg.str());
+		const size_t n = error_addons.size();
+		const std::string& msg1 =
+			_n("The following add-on had errors and could not be loaded:",
+			   "The following add-ons had errors and could not be loaded:",
+			   n);
+		const std::string& msg2 =
+			_n("Please report this to the author or maintainer of this add-on.",
+			   "Please report this to the respective authors or maintainers of these add-ons.",
+			   n);
+
+		const std::string& report = utils::join(error_log, "\n\n");
+
+		gui2::twml_error::display(msg1, msg2, error_addons, report,
+								  disp_.video());
 	}
 }
 
diff --git a/src/gui/dialogs/wml_error.cpp b/src/gui/dialogs/wml_error.cpp
new file mode 100644
index 000000000000..665b4cf88092
--- /dev/null
+++ b/src/gui/dialogs/wml_error.cpp
@@ -0,0 +1,236 @@
+/*
+   Copyright (C) 2014 by Ignacio R. Morelle <shadowm2006@gmail.com>
+   Part of the Battle for Wesnoth Project http://www.wesnoth.org/
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY.
+
+   See the COPYING file for more details.
+*/
+
+#define GETTEXT_DOMAIN "wesnoth-lib"
+
+#include "gui/dialogs/wml_error.hpp"
+
+#include "addon/info.hpp"
+#include "addon/manager.hpp"
+#include "clipboard.hpp"
+#include "filesystem.hpp"
+#include "gettext.hpp"
+#include "gui/auxiliary/find_widget.tpp"
+#include "gui/widgets/button.hpp"
+#include "gui/widgets/control.hpp"
+#include "gui/widgets/settings.hpp"
+#include "gui/widgets/window.hpp"
+#include "serialization/string_utils.hpp"
+
+#include <boost/bind.hpp>
+
+namespace
+{
+inline bool is_dir_separator(char c)
+{
+#ifdef _WIN32
+	return c == '/' || c == '\\';
+#else
+	return c == '/';
+#endif
+}
+
+void strip_trailing_dir_separators(std::string& str)
+{
+	while(is_dir_separator(str[str.size() - 1])) {
+		str.erase(str.size() - 1);
+	}
+}
+
+std::string format_file_list(const std::vector<std::string>& files_original)
+{
+	if(files_original.empty()) {
+		return "";
+	}
+
+	const std::string& addons_path = get_addon_campaigns_dir();
+	std::vector<std::string> files(files_original);
+
+	BOOST_FOREACH(std::string& file, files)
+	{
+		std::string base;
+		std::string filename = file_name(file);
+		std::string parent_path;
+
+		const bool is_main_cfg = filename == "_main.cfg";
+
+		if(is_main_cfg) {
+			parent_path = directory_name(file) + "/..";
+		} else {
+			parent_path = directory_name(file);
+		}
+
+		// Only proceed to pretty-format the filename if it's from the add-ons
+		// directory.
+		if(normalize_path(parent_path) != normalize_path(addons_path)) {
+			continue;
+		}
+
+		if(is_main_cfg) {
+			base = directory_name(file);
+			// HACK: fool file_name() into giving us the parent directory name
+			//       alone by making base seem not like a directory path,
+			//       otherwise it returns an empty string.
+			strip_trailing_dir_separators(base);
+			base = file_name(base);
+		} else {
+			base = filename;
+		}
+
+		if(base.empty()) {
+			// We did something wrong. In the interest of not messing up the
+			// report, leave the original filename intact.
+			continue;
+		}
+
+		//
+		// Display the name as an add-on name instead of a filename.
+		//
+
+		if(!is_main_cfg) {
+			// Remove the file extension first.
+			static const std::string wml_suffix = ".cfg";
+
+			if(base.size() > wml_suffix.size()) {
+				const size_t suffix_pos = base.size() - wml_suffix.size();
+				if(base.substr(suffix_pos) == wml_suffix) {
+					base.erase(suffix_pos);
+				}
+			}
+		}
+
+		if(have_addon_install_info(base)) {
+			// _info.cfg may have the add-on's title starting with 1.11.7,
+			// if the add-on was downloaded using the revised _info.cfg writer.
+			config cfg;
+			get_addon_install_info(base, cfg);
+
+			const config& info_cfg = cfg.child("info");
+
+			if(info_cfg) {
+				file = info_cfg["title"].str();
+				continue;
+			}
+		}
+
+		// Fallback to using a synthetic title with underscores replaced with
+		// whitespace.
+		file = make_addon_title(base);
+	}
+
+	if(files.size() == 1) {
+		return utils::indent(files.front());
+	}
+
+	return utils::bullet_list(files);
+}
+
+}
+
+namespace gui2
+{
+
+/*WIKI
+ * @page = GUIWindowDefinitionWML
+ * @order = 2_wml_error
+ *
+ * == WML error ==
+ *
+ * Dialog used to report WML parser or preprocessor errors.
+ *
+ * @begin{table}{dialog_widgets}
+ *
+ * summary & & control & m &
+ *         Label used for displaying a brief summary of the error(s). $
+ *
+ * files & & control & m &
+ *         Label used to display the list of affected add-ons or files, if
+ *         applicable. It is hidden otherwise. It is recommended to place it
+ *         after the summary label. $
+ *
+ * post_summary & & control & m &
+ *         Label used for displaying instructions for reporting the error.
+ *         It is recommended to place it after the file list label. It may be
+ *         hidden if empty. $
+ *
+ * details & & control & m &
+ *         Full report of the parser or preprocessor error(s) found. $
+ *
+ * copy & & button & m &
+ *         Button that the user can click on to copy the error report to the
+ *         system clipboard. $
+ *
+ * @end{table}
+ */
+
+REGISTER_DIALOG(wml_error)
+
+twml_error::twml_error(const std::string& summary,
+					   const std::string& post_summary,
+					   const std::vector<std::string>& files,
+					   const std::string& details)
+	: have_files_(!files.empty())
+	, have_post_summary_(!post_summary.empty())
+	, report_()
+{
+	const std::string& file_list_text = format_file_list(files);
+
+	report_ = summary;
+
+	if(!file_list_text.empty()) {
+		report_ += "\n" + file_list_text;
+	}
+
+	if(!post_summary.empty()) {
+		report_ += "\n\n" + post_summary;
+	}
+
+	report_ += "\n\n";
+	report_ += _("Details:");
+	report_ += "\n\n" + utils::indent(details);
+	// Since this is likely to be pasted into a text file, add a final line
+	// break for convenience, since otherwise the report ends mid-line.
+	report_ += "\n";
+
+	register_label("summary", true, summary);
+	register_label("post_summary", true, post_summary);
+	register_label("files", true, file_list_text);
+	register_label("details", true, details);
+}
+
+void twml_error::pre_show(CVideo& /*video*/, twindow& window)
+{
+    if(!have_files_) {
+		tcontrol& filelist = find_widget<tcontrol>(&window, "files", false);
+		filelist.set_visible(tcontrol::tvisible::invisible);
+	}
+
+	if(!have_post_summary_) {
+		tcontrol& post_summary = find_widget<tcontrol>(&window,
+													   "post_summary", false);
+		post_summary.set_visible(tcontrol::tvisible::invisible);
+	}
+
+	tbutton& copy_button = find_widget<tbutton>(&window, "copy", false);
+
+	connect_signal_mouse_left_click(
+			copy_button, boost::bind(&twml_error::copy_report_callback, this));
+}
+
+void twml_error::copy_report_callback()
+{
+	copy_to_clipboard(report_, false);
+}
+
+} // end namespace gui2
diff --git a/src/gui/dialogs/wml_error.hpp b/src/gui/dialogs/wml_error.hpp
new file mode 100644
index 000000000000..ad2b93de3287
--- /dev/null
+++ b/src/gui/dialogs/wml_error.hpp
@@ -0,0 +1,74 @@
+/*
+   Copyright (C) 2014 by Ignacio R. Morelle <shadowm2006@gmail.com>
+   Part of the Battle for Wesnoth Project http://www.wesnoth.org/
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY.
+
+   See the COPYING file for more details.
+*/
+
+#ifndef GUI_DIALOGS_WML_ERROR_HPP_INCLUDED
+#define GUI_DIALOGS_WML_ERROR_HPP_INCLUDED
+
+#include "gui/dialogs/dialog.hpp"
+
+namespace gui2 {
+
+/** WML preprocessor/parser error report dialog. */
+class twml_error : public tdialog
+{
+public:
+	/**
+	 * Constructor.
+	 *
+	 * @param summary      Leading summary line for the report.
+	 * @param post_summary Additional line with instructions for the user, may
+	 *                     be empty.
+	 * @param files        List of WML files on which errors were detected.
+	 * @param details      Detailed WML preprocessor/parser error report.
+	 */
+    twml_error(const std::string& summary,
+			   const std::string& post_summary,
+			   const std::vector<std::string>& files,
+			   const std::string& details);
+
+	/** The display function; see @ref tdialog for more information. */
+	static void display(const std::string& summary,
+						const std::string& post_summary,
+						const std::vector<std::string>& files,
+						const std::string& details,
+						CVideo& video)
+	{
+		twml_error(summary, post_summary, files, details).show(video);
+	}
+
+	/** The display function; see @ref tdialog for more information. */
+	static void display(const std::string& summary,
+						const std::string& details,
+						CVideo& video)
+	{
+		display(summary, "", std::vector<std::string>(), details, video);
+	}
+
+private:
+	bool have_files_;
+	bool have_post_summary_;
+	std::string report_; // Plain text report for copying to clipboard.
+
+	/** Inherited from tdialog, implemented by REGISTER_DIALOG. */
+	virtual const std::string& window_id() const;
+
+	/** Inherited from tdialog. */
+	void pre_show(CVideo& video, twindow& window);
+
+	void copy_report_callback();
+};
+
+}  // end namespace gui2
+
+#endif
diff --git a/src/serialization/parser.cpp b/src/serialization/parser.cpp
index 909e797a7508..9991fce612e0 100644
--- a/src/serialization/parser.cpp
+++ b/src/serialization/parser.cpp
@@ -64,7 +64,7 @@ class parser
 	void parse_element();
 	void parse_variable();
 	std::string lineno_string(utils::string_map &map, std::string const &lineno,
-		const char *error_string);
+		const char *error_string, const char *hint_string = NULL);
 	void error(const std::string& message);
 
 	config& cfg_;
@@ -142,7 +142,8 @@ void parser::operator()()
 		std::stringstream ss;
 		ss << elements.top().start_line << " " << elements.top().file;
 		error(lineno_string(i18n_symbols, ss.str(),
-				N_("Missing closing tag for tag [$tag] at $pos")));
+				N_("Missing closing tag for tag [$tag]"),
+				N_("at $pos")));
 	}
 }
 
@@ -205,7 +206,8 @@ void parser::parse_element()
 			std::stringstream ss;
 			ss << elements.top().start_line << " " << elements.top().file;
 			error(lineno_string(i18n_symbols, ss.str(),
-					N_("Found invalid closing tag [/$tag2] for tag [$tag1] (opened at $pos)")));
+					N_("Found invalid closing tag [/$tag2] for tag [$tag1]"),
+					N_("opened at $pos")));
 		}
 		if(validator_){
 			element & el= elements.top();
@@ -339,10 +341,18 @@ void parser::parse_variable()
  * This function is crap. Don't use it on a string_map with prefixes.
  */
 std::string parser::lineno_string(utils::string_map &i18n_symbols,
-	std::string const &lineno, const char *error_string)
+								  std::string const &lineno,
+								  const char *error_string,
+								  const char *hint_string)
 {
 	i18n_symbols["pos"] = ::lineno_string(lineno);
 	std::string result = _(error_string);
+
+	if(hint_string != NULL) {
+		result += "\n    ";
+		result += hint_string;
+	}
+
 	BOOST_FOREACH(utils::string_map::value_type& var, i18n_symbols)
 		boost::algorithm::replace_all(result, std::string("$") + var.first, std::string(var.second));
 	return result;
@@ -352,18 +362,18 @@ void parser::error(const std::string& error_type)
 {
 	utils::string_map i18n_symbols;
 	i18n_symbols["error"] = error_type;
-	i18n_symbols["value"] = tok_->current_token().value;
 	std::stringstream ss;
 	ss << tok_->get_start_line() << " " << tok_->get_file();
 #ifdef DEBUG
+	i18n_symbols["value"] = tok_->current_token().value;
 	i18n_symbols["previous_value"] = tok_->previous_token().value;
 	throw config::error(
 		lineno_string(i18n_symbols, ss.str(),
-		              N_("$error, value '$value', previous '$previous_value' at $pos")));
+		              N_("$error"), N_("at $pos (value '$value', previous '$previous_value')")));
 #else
 	throw config::error(
 		lineno_string(i18n_symbols, ss.str(),
-		              N_("$error, value '$value' at $pos")));
+		              N_("$error"), N_("at $pos")));
 #endif
 }
 
diff --git a/src/serialization/preprocessor.cpp b/src/serialization/preprocessor.cpp
index 08c2d35f313d..a46de77ddcb4 100644
--- a/src/serialization/preprocessor.cpp
+++ b/src/serialization/preprocessor.cpp
@@ -55,6 +55,8 @@ static t_file_number_map file_number_map;
 
 static bool encode_filename = true;
 
+static std::string preprocessor_error_detail_prefix = "\n    ";
+
 // get filename associated to this code
 static std::string get_filename(const std::string& file_code){
 	if(!encode_filename)
@@ -326,7 +328,8 @@ std::string lineno_string(const std::string &lineno)
 {
 	std::vector< std::string > pos = utils::quoted_split(lineno, ' ');
 	std::vector< std::string >::const_iterator i = pos.begin(), end = pos.end();
-	std::string included_from = " included from ";
+	std::string included_from =
+		preprocessor_error_detail_prefix + "included from ";
 	std::string res;
 	while (i != end) {
 		std::string const &line = *(i++);
@@ -348,7 +351,7 @@ void preprocessor_streambuf::error(const std::string& error_type, int l)
 	std::ostringstream pos;
 	pos << l << ' ' << location_;
 	position = lineno_string(pos.str());
-	error = error_type + " at " + position;
+	error = error_type + preprocessor_error_detail_prefix + "at " + position;
 	ERR_CF << error << '\n';
 	throw preproc_config::error(error);
 }
diff --git a/src/serialization/string_utils.cpp b/src/serialization/string_utils.cpp
index f86a008256fe..7c02dab549e0 100644
--- a/src/serialization/string_utils.cpp
+++ b/src/serialization/string_utils.cpp
@@ -741,6 +741,35 @@ bool wildcard_string_match(const std::string& str, const std::string& match) {
 	return matches;
 }
 
+std::string indent(const std::string& string, size_t indent_size)
+{
+	if(string.empty() || indent_size == 0) {
+		return "";
+	}
+
+	const std::string indent(indent_size, ' ');
+
+	const std::vector<std::string>& lines = split(string, '\x0A', 0);
+	std::string res;
+
+	for(size_t lno = 0; lno < lines.size();) {
+		const std::string& line = lines[lno];
+
+		// Lines containing only a carriage return count as empty.
+		if(!line.empty() && line != "\x0D") {
+			res += indent;
+		}
+
+		res += line;
+
+		if(++lno < lines.size()) {
+			res += '\x0A';
+		}
+	}
+
+	return res;
+}
+
 std::vector< std::string > quoted_split(std::string const &val, char c, int flags, char quote)
 {
 	std::vector<std::string> res;
diff --git a/src/serialization/string_utils.hpp b/src/serialization/string_utils.hpp
index 42e9f81f813c..abfb82e203fd 100644
--- a/src/serialization/string_utils.hpp
+++ b/src/serialization/string_utils.hpp
@@ -191,6 +191,17 @@ std::string bullet_list(const T& v, size_t indent = 4, const std::string& bullet
 	return str.str();
 }
 
+/**
+ * Indent a block of text.
+ *
+ * Only lines with content are changed; empty lines are left intact.
+ *
+ * @param string      Text to indent.
+ * @param indent_size Number of indentation units to use.
+ * @param indent_unit Indentation unit.
+ */
+std::string indent(const std::string& string, size_t indent_size = 4);
+
 /**
  * This function is identical to split(), except it does not split
  * when it otherwise would if the previous character was identical to the parameter 'quote'.