diff --git a/rwgame/GameConfig.cpp b/rwgame/GameConfig.cpp
index 89291e24..b781c123 100644
--- a/rwgame/GameConfig.cpp
+++ b/rwgame/GameConfig.cpp
@@ -1,16 +1,16 @@
 #include "GameConfig.hpp"
-#include <cstdlib>
-#include <cstring>
+#include <algorithm>
+
 #include <rw/defines.hpp>
 
-#include <boost/property_tree/ptree.hpp>
 #include <boost/property_tree/ini_parser.hpp>
+#include <boost/property_tree/ptree.hpp>
 namespace pt = boost::property_tree;
 
 const std::string kConfigDirectoryName("OpenRW");
 
-GameConfig::GameConfig(const std::string& configName,
-                       const std::string& configPath)
+GameConfig::GameConfig(const std::string &configName,
+                       const std::string &configPath)
     : m_configName(configName)
     , m_configPath(configPath)
     , m_parseResult()
@@ -23,7 +23,8 @@ GameConfig::GameConfig(const std::string& configName,
     auto configFile = getConfigFile();
 
     std::string dummy;
-    m_parseResult = parseConfig(ParseType::FILE, configFile, ParseType::CONFIG, dummy);
+    m_parseResult =
+        parseConfig(ParseType::FILE, configFile, ParseType::CONFIG, dummy);
 }
 
 std::string GameConfig::getConfigFile() const {
@@ -41,17 +42,17 @@ const GameConfig::ParseResult &GameConfig::getParseResult() const {
 std::string GameConfig::getDefaultConfigPath() {
 #if defined(RW_LINUX) || defined(RW_FREEBSD) || defined(RW_NETBSD) || \
     defined(RW_OPENBSD)
-    char* config_home = getenv("XDG_CONFIG_HOME");
+    char *config_home = getenv("XDG_CONFIG_HOME");
     if (config_home != nullptr) {
         return std::string(config_home) + "/" + kConfigDirectoryName;
     }
-    char* home = getenv("HOME");
+    char *home = getenv("HOME");
     if (home != nullptr) {
         return std::string(home) + "/.config/" + kConfigDirectoryName;
     }
 
 #elif defined(RW_OSX)
-    char* home = getenv("HOME");
+    char *home = getenv("HOME");
     if (home)
         return std::string(home) + "/Library/Preferences/" +
                kConfigDirectoryName;
@@ -67,7 +68,7 @@ std::string GameConfig::getDefaultConfigPath() {
 
 std::string stripComments(const std::string &str) {
     auto s = std::string(str, 0, str.find_first_of(";#"));
-    return s.erase(s.find_last_not_of(" \n\r\t")+1);
+    return s.erase(s.find_last_not_of(" \n\r\t") + 1);
 }
 
 struct StringTranslator {
@@ -83,7 +84,7 @@ struct StringTranslator {
 
 struct BoolTranslator {
     typedef std::string internal_type;
-    typedef bool        external_type;
+    typedef bool external_type;
     boost::optional<external_type> get_value(const internal_type &str) {
         boost::optional<external_type> res;
         try {
@@ -99,7 +100,7 @@ struct BoolTranslator {
 
 struct IntTranslator {
     typedef std::string internal_type;
-    typedef int         external_type;
+    typedef int external_type;
     boost::optional<external_type> get_value(const internal_type &str) {
         boost::optional<external_type> res;
         try {
@@ -115,8 +116,7 @@ struct IntTranslator {
 
 GameConfig::ParseResult GameConfig::saveConfig() {
     auto filename = getConfigFile();
-    return parseConfig(ParseType::CONFIG, "",
-        ParseType::FILE, filename);
+    return parseConfig(ParseType::CONFIG, "", ParseType::FILE, filename);
 }
 
 std::string GameConfig::getDefaultINIString() {
@@ -125,10 +125,11 @@ std::string GameConfig::getDefaultINIString() {
     return result;
 }
 
-GameConfig::ParseResult GameConfig::parseConfig(
-    GameConfig::ParseType srcType, const std::string &source,
-    ParseType destType, std::string &destination)
-{
+GameConfig::ParseResult GameConfig::parseConfig(GameConfig::ParseType srcType,
+                                                const std::string &source,
+                                                ParseType destType,
+                                                std::string &destination) {
+    // srcTree: holds all key/value pairs
     pt::ptree srcTree;
     ParseResult parseResult(srcType, source, destType, destination);
 
@@ -152,12 +153,16 @@ GameConfig::ParseResult GameConfig::parseConfig(
         return parseResult;
     }
 
+    // knownKeys: holds all known keys
+    std::vector<std::string> knownKeys;
+
     auto read_config = [&](const std::string &key, auto &target,
-                          const auto &defaultValue, auto &translator,
-                          bool optional=true) {
+                           const auto &defaultValue, auto &translator,
+                           bool optional = true) {
         typedef typename std::remove_reference<decltype(target)>::type config_t;
 
         config_t sourceValue;
+        knownKeys.push_back(key);
 
         switch (srcType) {
             case ParseType::DEFAULT:
@@ -210,13 +215,50 @@ GameConfig::ParseResult GameConfig::parseConfig(
     // Additionally, add them to the unit test.
 
     // @todo Don't allow path separators and relative directories
-    read_config("game.path", this->m_gamePath, "/opt/games/Grand Theft Auto 3", deft, false);
+    read_config("game.path", this->m_gamePath, "/opt/games/Grand Theft Auto 3",
+                deft, false);
     read_config("game.language", this->m_gameLanguage, "american", deft);
 
     read_config("input.invert_y", this->m_inputInvertY, false, boolt);
 
-    if (!parseResult.isValid())
-        return parseResult;
+    if (!parseResult.isValid()) return parseResult;
+
+    // Build the unknown key/value map from the correct source
+    switch (srcType) {
+        case ParseType::FILE:
+        case ParseType::STRING:
+            for (const auto &section : srcTree) {
+                for (const auto &subKey : section.second) {
+                    std::string key = section.first + "." + subKey.first;
+                    if (std::find(knownKeys.begin(), knownKeys.end(), key) ==
+                        knownKeys.end()) {
+                        RW_MESSAGE("Unknown configuration key: " << key);
+                        parseResult.addUnknownData(key, subKey.second.data());
+                    }
+                }
+            }
+            break;
+        case ParseType::CONFIG:
+            parseResult.setUnknownData(m_parseResult.getUnknownData());
+            break;
+        case ParseType::DEFAULT:
+            break;
+    }
+
+    // Store the unknown key/value map to the correct destination
+    switch (destType) {
+        case ParseType::CONFIG:
+            m_parseResult.setUnknownData(parseResult.getUnknownData());
+            break;
+        case ParseType::STRING:
+        case ParseType::FILE:
+            for (const auto &keyvalue : parseResult.getUnknownData()) {
+                srcTree.put(keyvalue.first, keyvalue.second);
+            }
+            break;
+        default:
+            break;
+    }
 
     try {
         if (destType == ParseType::STRING) {
@@ -234,8 +276,8 @@ GameConfig::ParseResult GameConfig::parseConfig(
     return parseResult;
 }
 
-std::string GameConfig::extractFilenameParseTypeData(ParseType type, const std::string &data)
-{
+std::string GameConfig::extractFilenameParseTypeData(ParseType type,
+                                                     const std::string &data) {
     switch (type) {
         case ParseType::CONFIG:
             return "<configuration>";
@@ -249,16 +291,19 @@ std::string GameConfig::extractFilenameParseTypeData(ParseType type, const std::
     }
 }
 
-GameConfig::ParseResult::ParseResult(
-            GameConfig::ParseType srcType, const std::string &source,
-            GameConfig::ParseType destType, const std::string &destination)
+GameConfig::ParseResult::ParseResult(GameConfig::ParseType srcType,
+                                     const std::string &source,
+                                     GameConfig::ParseType destType,
+                                     const std::string &destination)
     : m_result(ErrorType::GOOD)
     , m_inputfilename(GameConfig::extractFilenameParseTypeData(srcType, source))
-    , m_outputfilename(GameConfig::extractFilenameParseTypeData(destType, destination))
+    , m_outputfilename(
+          GameConfig::extractFilenameParseTypeData(destType, destination))
     , m_line(0)
     , m_message()
     , m_keys_requiredMissing()
-    , m_keys_invalidData() {
+    , m_keys_invalidData()
+    , m_unknownData() {
 }
 
 GameConfig::ParseResult::ParseResult()
@@ -280,7 +325,7 @@ bool GameConfig::ParseResult::isValid() const {
 }
 
 void GameConfig::ParseResult::failInputFile(size_t line,
-        const std::string &message) {
+                                            const std::string &message) {
     this->m_result = ParseResult::ErrorType::INVALIDINPUTFILE;
     this->m_line = line;
     this->m_message = message;
@@ -301,17 +346,19 @@ void GameConfig::ParseResult::failInvalidData(const std::string &key) {
 }
 
 void GameConfig::ParseResult::failOutputFile(size_t line,
-        const std::string &message) {
+                                             const std::string &message) {
     this->m_result = ParseResult::ErrorType::INVALIDOUTPUTFILE;
     this->m_line = line;
     this->m_message = message;
 }
 
-const std::vector<std::string> &GameConfig::ParseResult::getKeysRequiredMissing() const {
+const std::vector<std::string>
+    &GameConfig::ParseResult::getKeysRequiredMissing() const {
     return this->m_keys_requiredMissing;
 }
 
-const std::vector<std::string> &GameConfig::ParseResult::getKeysInvalidData() const {
+const std::vector<std::string> &GameConfig::ParseResult::getKeysInvalidData()
+    const {
     return this->m_keys_invalidData;
 }
 
@@ -321,27 +368,23 @@ std::string GameConfig::ParseResult::what() const {
             return "Good";
         case ErrorType::INVALIDARGUMENT:
             return "Invalid argument: destination cannot be the default config";
-        case ErrorType::INVALIDINPUTFILE:
-        {
+        case ErrorType::INVALIDINPUTFILE: {
             std::ostringstream oss;
-            oss << "Error while reading \"" 
-                << this->m_inputfilename << "\":" << this->m_line << ":\n"
+            oss << "Error while reading \"" << this->m_inputfilename
+                << "\":" << this->m_line << ":\n"
                 << this->m_message;
             return oss.str();
         }
-        case ErrorType::INVALIDOUTPUTFILE:
-        {
+        case ErrorType::INVALIDOUTPUTFILE: {
             std::ostringstream oss;
-            oss << "Error while writing \"" 
-                << this->m_inputfilename << "\":" << this->m_line << ":\n"
+            oss << "Error while writing \"" << this->m_inputfilename
+                << "\":" << this->m_line << ":\n"
                 << this->m_message;
             return oss.str();
         }
-        case ErrorType::INVALIDCONTENT:
-        {
+        case ErrorType::INVALIDCONTENT: {
             std::ostringstream oss;
-            oss << "Error while parsing \"" 
-                << this->m_inputfilename << "\".";
+            oss << "Error while parsing \"" << this->m_inputfilename << "\".";
             if (this->m_keys_requiredMissing.size()) {
                 oss << "\nRequired keys that are missing:";
                 for (auto &key : this->m_keys_requiredMissing) {
@@ -360,3 +403,18 @@ std::string GameConfig::ParseResult::what() const {
             return "Unknown error";
     }
 }
+
+void GameConfig::ParseResult::addUnknownData(const std::string &key,
+                                             const std::string &value) {
+    this->m_unknownData[key] = value;
+}
+
+const std::map<std::string, std::string>
+    &GameConfig::ParseResult::getUnknownData() const {
+    return this->m_unknownData;
+}
+
+void GameConfig::ParseResult::setUnknownData(
+    const std::map<std::string, std::string> &unknownData) {
+    this->m_unknownData = unknownData;
+}
diff --git a/rwgame/GameConfig.hpp b/rwgame/GameConfig.hpp
index 51a24522..732101b1 100644
--- a/rwgame/GameConfig.hpp
+++ b/rwgame/GameConfig.hpp
@@ -1,47 +1,50 @@
 #ifndef RWGAME_GAMECONFIG_HPP
 #define RWGAME_GAMECONFIG_HPP
+#include <map>
 #include <string>
 #include <vector>
 
 class GameConfig {
 private:
-    enum ParseType {
-        DEFAULT,
-        CONFIG,
-        FILE,
-        STRING
-    };
+    enum ParseType { DEFAULT, CONFIG, FILE, STRING };
 
     /**
      * @brief extractFilenameParseTypeData Get a human readable filename string
      * @return file path or a description of the data type
      */
-    static std::string extractFilenameParseTypeData(ParseType type, const std::string &data);
+    static std::string extractFilenameParseTypeData(ParseType type,
+                                                    const std::string &data);
+
 public:
     class ParseResult {
     public:
         enum ErrorType {
             /// GOOD: Input file/string was good
             GOOD,
-            /// INVALIDINPUTFILE: There was some error while reading from a file or string or the input was ambiguous (e.g. duplicate keys)
+            /// INVALIDINPUTFILE: There was some error while reading from a file
+            /// or string or the input was ambiguous (e.g. duplicate keys)
             INVALIDINPUTFILE,
             /// INVALIDARGUMENT: The parser received impossible arguments
             INVALIDARGUMENT,
-            /// INVALIDCONTENT: Some required keys were missing or some values were of incorrect type
+            /// INVALIDCONTENT: Some required keys were missing or some values
+            /// were of incorrect type
             INVALIDCONTENT,
-            /// INVALIDOUTPUTFILE: There was some error while writing to a file or string
+            /// INVALIDOUTPUTFILE: There was some error while writing to a file
+            /// or string
             INVALIDOUTPUTFILE
         };
+
     private:
         /**
-         * @brief ParseResult Holds the issues occurred while parsing of a config file.
+         * @brief ParseResult Holds the issues occurred while parsing of a
+         * config file.
          * @param srcType Type of the source
          * @param source The source of the parser
          * @param destType Type of the destination
          * @param destination The destination
          */
         ParseResult(ParseType srcType, const std::string &source,
-            ParseType destType, const std::string &destination);
+                    ParseType destType, const std::string &destination);
 
         /**
          * @brief ParseResult Create empty ParseResult
@@ -93,7 +96,8 @@ public:
         void failInvalidData(const std::string &key);
 
         /**
-         * @brief failOutputFile Fail because an error occurred while while writing to the output
+         * @brief failOutputFile Fail because an error occurred while while
+         * writing to the output
          * @param line Line number where the error is located
          * @param message Description of the error
          */
@@ -110,6 +114,20 @@ public:
          * @return String with the error description
          */
         std::string what() const;
+
+        /**
+         * @brief addUnknownData Add unknown key value pairs
+         * @param key The unknown key
+         * @param value The associated data
+         */
+        void addUnknownData(const std::string &key, const std::string &value);
+
+        /**
+         * @brief addUnknownData Get all the unknown key value pairs
+         * @return Mapping of the unknown keys with associated data
+         */
+        const std::map<std::string, std::string> &getUnknownData() const;
+
     private:
         /// Type of the failure
         ErrorType m_result;
@@ -120,7 +138,8 @@ public:
         /// Filename of the output file
         std::string m_outputfilename;
 
-        /// Line number where the failure occurred (on invalid input or output file)
+        /// Line number where the failure occurred (on invalid input or output
+        /// file)
         size_t m_line;
 
         /// Description of the failure (on invalid input or output file)
@@ -132,6 +151,15 @@ public:
         /// All keys that contain invalid data
         std::vector<std::string> m_keys_invalidData;
 
+        // Mapping of unknown keys and associated data
+        std::map<std::string, std::string> m_unknownData;
+
+        /**
+         * @brief setUnknownData Replace the the unknown key value pairs
+         */
+        void setUnknownData(
+            const std::map<std::string, std::string> &unknownData);
+
         friend class GameConfig;
     };
 
@@ -140,8 +168,8 @@ public:
      * @param configName The configuration filename to load
      * @param configPath Where to look.
      */
-    GameConfig(const std::string& configName,
-               const std::string& configPath = getDefaultConfigPath());
+    GameConfig(const std::string &configName,
+               const std::string &configPath = getDefaultConfigPath());
 
     /**
      * @brief getFilePath Returns the system file path for the configuration
@@ -166,15 +194,16 @@ public:
     const ParseResult &getParseResult() const;
 
     /**
-     * @brief getConfigString Returns the content of the default INI configuration.
+     * @brief getConfigString Returns the content of the default INI
+     * configuration.
      * @return INI string
      */
     std::string getDefaultINIString();
 
-    const std::string& getGameDataPath() const {
+    const std::string &getGameDataPath() const {
         return m_gamePath;
     }
-    const std::string& getGameLanguage() const {
+    const std::string &getGameLanguage() const {
         return m_gameLanguage;
     }
     bool getInputInvertY() const {
@@ -186,6 +215,7 @@ private:
 
     /**
      * @brief parseConfig Load data from source and write it to destination.
+     * Whitespace will be stripped from unknown data.
      * @param srcType Can be DEFAULT | CONFIG | FILE | STRING
      * @param source don't care if srcType == (DEFAULT | CONFIG),
      *               path of INI file if srcType == FILE
@@ -197,7 +227,7 @@ private:
      * @return True if the parsing succeeded
      */
     ParseResult parseConfig(ParseType srcType, const std::string &source,
-        ParseType destType, std::string &destination);
+                            ParseType destType, std::string &destination);
 
     /* Config State */
     std::string m_configName;
diff --git a/tests/test_config.cpp b/tests/test_config.cpp
index d73fce1f..51b636e1 100644
--- a/tests/test_config.cpp
+++ b/tests/test_config.cpp
@@ -3,12 +3,39 @@
 #include <boost/filesystem.hpp>
 #include <boost/test/unit_test.hpp>
 
+#include <boost/property_tree/ini_parser.hpp>
+#include <boost/property_tree/ptree.hpp>
+
 #include <fstream>
 #include <map>
 
+#include "rw/defines.hpp"
+
+namespace pt = boost::property_tree;
 namespace fs = boost::filesystem;
 
-typedef std::map<std::string, std::map<std::string, std::string>> simpleConfig_t;
+typedef std::map<std::string, std::map<std::string, std::string>>
+    simpleConfig_t;
+
+simpleConfig_t readConfig(const std::string &filename) {
+    simpleConfig_t cfg;
+    pt::ptree tree;
+    pt::read_ini(filename, tree);
+
+    for (const auto &section : tree) {
+        for (const auto &subKey : section.second) {
+            cfg[section.first][subKey.first] = subKey.second.data();
+        }
+    }
+    return cfg;
+}
+
+std::string stripWhitespace(const std::string &in) {
+    static const std::string whitespace = " \n\r\t";
+    auto start = in.find_first_not_of(whitespace);
+    auto end = in.find_last_not_of(whitespace) + 1;
+    return std::string(in, start, end - start);
+}
 
 simpleConfig_t getValidConfig() {
     simpleConfig_t result;
@@ -16,14 +43,17 @@ simpleConfig_t getValidConfig() {
     // to test the robustness of the INI parser.
     // Don't change game.path and input.invert_y keys. Tests depend on them.
     result["game"]["path"] = "\t/dev/test  \t \r\n";
-    result["game"]["\tlanguage\t "] = "      american ;american english french german italian spanish.";
-    result["input"]["invert_y"] = "1 #values != 0 enable input inversion. Optional.";
+    result["game"]["\tlanguage\t "] =
+        "      american ;american english french german italian spanish.";
+    result["input"]["invert_y"] =
+        "1 #values != 0 enable input inversion. Optional.";
     return result;
 }
 
 std::ostream &operator<<(std::ostream &os, const simpleConfig_t &config) {
     for (auto &section : config) {
-        os << "[" << section.first << "]" << "\n";
+        os << "[" << section.first << "]"
+           << "\n";
         for (auto &keyValue : section.second) {
             os << keyValue.first << "=" << keyValue.second << "\n";
         }
@@ -59,10 +89,11 @@ public:
         return this->m_path.parent_path().string();
     }
     void change_perms_readonly() {
-        fs::permissions(this->m_path, fs::perms::owner_read
-            | fs::perms::group_read | fs::perms::others_read);
+        fs::permissions(this->m_path, fs::perms::owner_read |
+                                          fs::perms::group_read |
+                                          fs::perms::others_read);
     }
-    template<typename T>
+    template <typename T>
     bool append(T t) {
         // Append argument at the end of the file.
         // File is open/closes repeatedly. Not optimal.
@@ -71,7 +102,7 @@ public:
         ofs.close();
         return ofs.good();
     }
-    template<typename T>
+    template <typename T>
     bool write(T t) {
         // Write the argument to the file, discarding all contents.
         // File is open/closes repeatedly. Not optimal.
@@ -80,15 +111,31 @@ public:
         ofs.close();
         return ofs.good();
     }
+
 private:
     static fs::path getRandomFilePath() {
-        return fs::unique_path(fs::temp_directory_path() / "openrw_test_%%%%%%%%%%%%%%%%");
+        return fs::unique_path(fs::temp_directory_path() /
+                               "openrw_test_%%%%%%%%%%%%%%%%");
     }
     fs::path m_path;
 };
 
 BOOST_AUTO_TEST_SUITE(ConfigTests)
 
+BOOST_AUTO_TEST_CASE(test_stripWhitespace) {
+    std::map<std::string, std::string> map;
+    map["abc"] = "abc";
+    map["\tabc"] = "abc";
+    map["abc\t"] = "abc";
+    map[" abc"] = "abc";
+    map["abc "] = "abc";
+    map[" abc "] = "abc";
+    map["  abc  "] = "abc";
+    for (const auto &keyValue : map) {
+        BOOST_CHECK_EQUAL(keyValue.second, stripWhitespace(keyValue.first));
+    }
+}
+
 BOOST_AUTO_TEST_CASE(test_TempFile) {
     // Check the behavior of TempFile
     TempFile tempFile;
@@ -126,8 +173,10 @@ BOOST_AUTO_TEST_CASE(test_config_valid) {
     GameConfig config(tempFile.filename(), tempFile.dirname());
 
     BOOST_CHECK(config.isValid());
-    BOOST_CHECK_EQUAL(config.getParseResult().type(), GameConfig::ParseResult::ErrorType::GOOD);
-    BOOST_CHECK_EQUAL(config.getParseResult().getKeysRequiredMissing().size(), 0);
+    BOOST_CHECK_EQUAL(config.getParseResult().type(),
+                      GameConfig::ParseResult::ErrorType::GOOD);
+    BOOST_CHECK_EQUAL(config.getParseResult().getKeysRequiredMissing().size(),
+                      0);
     BOOST_CHECK_EQUAL(config.getParseResult().getKeysInvalidData().size(), 0);
 
     BOOST_CHECK_EQUAL(config.getGameDataPath(), "/dev/test");
@@ -147,8 +196,10 @@ BOOST_AUTO_TEST_CASE(test_config_valid_modified) {
     GameConfig config(tempFile.filename(), tempFile.dirname());
 
     BOOST_CHECK(config.isValid());
-    BOOST_CHECK_EQUAL(config.getParseResult().type(), GameConfig::ParseResult::ErrorType::GOOD);
-    BOOST_CHECK_EQUAL(config.getParseResult().getKeysRequiredMissing().size(), 0);
+    BOOST_CHECK_EQUAL(config.getParseResult().type(),
+                      GameConfig::ParseResult::ErrorType::GOOD);
+    BOOST_CHECK_EQUAL(config.getParseResult().getKeysRequiredMissing().size(),
+                      0);
     BOOST_CHECK_EQUAL(config.getParseResult().getKeysInvalidData().size(), 0);
 
     BOOST_CHECK_EQUAL(config.getInputInvertY(), false);
@@ -176,6 +227,55 @@ BOOST_AUTO_TEST_CASE(test_config_save) {
 
     GameConfig config2(tempFile.filename(), tempFile.dirname());
     BOOST_CHECK_EQUAL(config2.getGameDataPath(), "Liberty City");
+
+    simpleConfig_t cfg2 = readConfig(tempFile.path());
+    BOOST_CHECK_EQUAL(cfg2["game"]["path"], "Liberty City");
+}
+
+BOOST_AUTO_TEST_CASE(test_config_valid_unknown_keys) {
+    // Test reading a valid modified configuration file with unknown data
+    auto cfg = getValidConfig();
+    cfg["game"]["unknownkey"] = "descartes";
+    cfg["dontknow"]["dontcare"] = "\t$%!$8847  %%$  ";
+
+    TempFile tempFile;
+    tempFile.append(cfg);
+
+    GameConfig config(tempFile.filename(), tempFile.dirname());
+
+    BOOST_CHECK(config.isValid());
+
+    const auto &unknownData = config.getParseResult().getUnknownData();
+
+    BOOST_CHECK_EQUAL(unknownData.size(), 2);
+
+    BOOST_CHECK_EQUAL(unknownData.count("game.unknownkey"), 1);
+    BOOST_CHECK_EQUAL(unknownData.at("game.unknownkey"),
+                      stripWhitespace(cfg["game"]["unknownkey"]));
+
+    BOOST_CHECK_EQUAL(unknownData.count("dontknow.dontcare"), 1);
+    BOOST_CHECK_EQUAL(unknownData.at("dontknow.dontcare"),
+                      stripWhitespace(cfg["dontknow"]["dontcare"]));
+
+    BOOST_CHECK_EQUAL(unknownData.count("game.path"), 0);
+
+    tempFile.remove();
+    config.saveConfig();
+
+    GameConfig config2(tempFile.filename(), tempFile.dirname());
+    const auto &unknownData2 = config2.getParseResult().getUnknownData();
+
+    BOOST_CHECK_EQUAL(unknownData2.size(), 2);
+
+    BOOST_CHECK_EQUAL(unknownData2.count("game.unknownkey"), 1);
+    BOOST_CHECK_EQUAL(unknownData2.at("game.unknownkey"),
+                      stripWhitespace(cfg["game"]["unknownkey"]));
+
+    BOOST_CHECK_EQUAL(unknownData2.count("dontknow.dontcare"), 1);
+    BOOST_CHECK_EQUAL(unknownData2.at("dontknow.dontcare"),
+                      stripWhitespace(cfg["dontknow"]["dontcare"]));
+
+    BOOST_CHECK_EQUAL(unknownData2.count("game.path"), 0);
 }
 
 BOOST_AUTO_TEST_CASE(test_config_save_readonly) {
@@ -191,7 +291,8 @@ BOOST_AUTO_TEST_CASE(test_config_save_readonly) {
 
     auto writeResult = config.saveConfig();
     BOOST_CHECK(!writeResult.isValid());
-    BOOST_CHECK_EQUAL(writeResult.type(), GameConfig::ParseResult::ErrorType::INVALIDOUTPUTFILE);
+    BOOST_CHECK_EQUAL(writeResult.type(),
+                      GameConfig::ParseResult::ErrorType::INVALIDOUTPUTFILE);
 }
 
 BOOST_AUTO_TEST_CASE(test_config_valid_default) {
@@ -209,6 +310,22 @@ BOOST_AUTO_TEST_CASE(test_config_valid_default) {
     BOOST_CHECK(config.isValid());
 }
 
+BOOST_AUTO_TEST_CASE(test_config_invalid_emptykey) {
+    // Test duplicate keys in invalid configuration file
+    auto cfg = getValidConfig();
+    cfg["game"][""] = "0";
+
+    TempFile tempFile;
+    tempFile.append(cfg);
+
+    GameConfig config(tempFile.filename(), tempFile.dirname());
+
+    BOOST_CHECK(!config.isValid());
+    const auto &parseResult = config.getParseResult();
+    BOOST_CHECK_EQUAL(parseResult.type(),
+                      GameConfig::ParseResult::ErrorType::INVALIDINPUTFILE);
+}
+
 BOOST_AUTO_TEST_CASE(test_config_invalid_duplicate) {
     // Test duplicate keys in invalid configuration file
     auto cfg = getValidConfig();
@@ -221,7 +338,8 @@ BOOST_AUTO_TEST_CASE(test_config_invalid_duplicate) {
 
     BOOST_CHECK(!config.isValid());
     const auto &parseResult = config.getParseResult();
-    BOOST_CHECK_EQUAL(parseResult.type(), GameConfig::ParseResult::ErrorType::INVALIDINPUTFILE);
+    BOOST_CHECK_EQUAL(parseResult.type(),
+                      GameConfig::ParseResult::ErrorType::INVALIDINPUTFILE);
 }
 
 BOOST_AUTO_TEST_CASE(test_config_invalid_required_missing) {
@@ -237,7 +355,8 @@ BOOST_AUTO_TEST_CASE(test_config_invalid_required_missing) {
     BOOST_CHECK(!config.isValid());
 
     const auto &parseResult = config.getParseResult();
-    BOOST_CHECK_EQUAL(parseResult.type(), GameConfig::ParseResult::ErrorType::INVALIDCONTENT);
+    BOOST_CHECK_EQUAL(parseResult.type(),
+                      GameConfig::ParseResult::ErrorType::INVALIDCONTENT);
 
     BOOST_CHECK_EQUAL(parseResult.getKeysRequiredMissing().size(), 1);
     BOOST_CHECK_EQUAL(parseResult.getKeysInvalidData().size(), 0);
@@ -248,7 +367,7 @@ BOOST_AUTO_TEST_CASE(test_config_invalid_required_missing) {
 BOOST_AUTO_TEST_CASE(test_config_invalid_wrong_type) {
     // Test wrong data type
     auto cfg = getValidConfig();
-    cfg["input"]["invert_y"]="d";
+    cfg["input"]["invert_y"] = "d";
 
     TempFile tempFile;
     tempFile.append(cfg);
@@ -258,7 +377,8 @@ BOOST_AUTO_TEST_CASE(test_config_invalid_wrong_type) {
     BOOST_CHECK(!config.isValid());
 
     const auto &parseResult = config.getParseResult();
-    BOOST_CHECK_EQUAL(parseResult.type(), GameConfig::ParseResult::ErrorType::INVALIDCONTENT);
+    BOOST_CHECK_EQUAL(parseResult.type(),
+                      GameConfig::ParseResult::ErrorType::INVALIDCONTENT);
 
     BOOST_CHECK_EQUAL(parseResult.getKeysRequiredMissing().size(), 0);
     BOOST_CHECK_EQUAL(parseResult.getKeysInvalidData().size(), 1);
@@ -268,7 +388,8 @@ BOOST_AUTO_TEST_CASE(test_config_invalid_wrong_type) {
 
 BOOST_AUTO_TEST_CASE(test_config_invalid_empty) {
     // Test reading empty configuration file
-    // An empty file has a valid data structure, but has missing keys and is thus invalid.
+    // An empty file has a valid data structure, but has missing keys and is
+    // thus invalid.
     TempFile tempFile;
     tempFile.touch();
     BOOST_CHECK(tempFile.exists());
@@ -278,7 +399,8 @@ BOOST_AUTO_TEST_CASE(test_config_invalid_empty) {
     BOOST_CHECK(!config.isValid());
 
     const auto &parseResult = config.getParseResult();
-    BOOST_CHECK_EQUAL(parseResult.type(), GameConfig::ParseResult::ErrorType::INVALIDCONTENT);
+    BOOST_CHECK_EQUAL(parseResult.type(),
+                      GameConfig::ParseResult::ErrorType::INVALIDCONTENT);
     BOOST_CHECK_GE(parseResult.getKeysRequiredMissing().size(), 1);
 }
 
@@ -292,7 +414,8 @@ BOOST_AUTO_TEST_CASE(test_config_invalid_nonexisting) {
     BOOST_CHECK(!config.isValid());
 
     const auto &parseResult = config.getParseResult();
-    BOOST_CHECK_EQUAL(parseResult.type(), GameConfig::ParseResult::ErrorType::INVALIDINPUTFILE);
+    BOOST_CHECK_EQUAL(parseResult.type(),
+                      GameConfig::ParseResult::ErrorType::INVALIDINPUTFILE);
 }
 
 BOOST_AUTO_TEST_SUITE_END()