diff --git a/perl/lib/Nix/Store.xs b/perl/lib/Nix/Store.xs
index bbfb2934..ce553bb5 100644
--- a/perl/lib/Nix/Store.xs
+++ b/perl/lib/Nix/Store.xs
@@ -27,7 +27,7 @@ static ref<Store> store()
     static std::shared_ptr<Store> _store;
     if (!_store) {
         try {
-            settings.loadConfFile();
+            loadConfFile();
             settings.lockCPU = false;
             _store = openStore();
         } catch (Error & e) {
diff --git a/src/libmain/common-args.cc b/src/libmain/common-args.cc
index bcc05c2c..4c35a419 100644
--- a/src/libmain/common-args.cc
+++ b/src/libmain/common-args.cc
@@ -29,14 +29,14 @@ MixCommonArgs::MixCommonArgs(const string & programName)
         .arity(2)
         .handler([](std::vector<std::string> ss) {
             try {
-                settings.set(ss[0], ss[1]);
+                globalConfig.set(ss[0], ss[1]);
             } catch (UsageError & e) {
                 warn(e.what());
             }
         });
 
     std::string cat = "config";
-    settings.convertToArgs(*this, cat);
+    globalConfig.convertToArgs(*this, cat);
 
     // Backward compatibility hack: nix-env already had a --system flag.
     if (programName == "nix-env") longFlags.erase("system");
diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index 91a4eaf9..4ed34e54 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -109,7 +109,7 @@ void initNix()
     opensslLocks = std::vector<std::mutex>(CRYPTO_num_locks());
     CRYPTO_set_locking_callback(opensslLockCallback);
 
-    settings.loadConfFile();
+    loadConfFile();
 
     startSignalHandlerThread();
 
diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index f70ab810..07b53378 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -672,8 +672,10 @@ HookInstance::HookInstance()
     toHook.readSide = -1;
 
     sink = FdSink(toHook.writeSide.get());
-    for (auto & setting : settings.getSettings())
-        sink << 1 << setting.first << setting.second;
+    std::map<std::string, Config::SettingInfo> settings;
+    globalConfig.getSettings(settings);
+    for (auto & setting : settings)
+        sink << 1 << setting.first << setting.second.value;
     sink << 0;
 }
 
diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index 544566e0..d95db567 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -28,9 +28,10 @@ namespace nix {
 
 Settings settings;
 
+static GlobalConfig::Register r1(&settings);
+
 Settings::Settings()
-    : Config({})
-    , nixPrefix(NIX_PREFIX)
+    : nixPrefix(NIX_PREFIX)
     , nixStore(canonPath(getEnv("NIX_STORE_DIR", getEnv("NIX_STORE", NIX_STORE_DIR))))
     , nixDataDir(canonPath(getEnv("NIX_DATA_DIR", NIX_DATA_DIR)))
     , nixLogDir(canonPath(getEnv("NIX_LOG_DIR", NIX_LOG_DIR)))
@@ -69,20 +70,15 @@ Settings::Settings()
     allowedImpureHostPrefixes = tokenizeString<StringSet>(DEFAULT_ALLOWED_IMPURE_PREFIXES);
 }
 
-void Settings::loadConfFile()
+void loadConfFile()
 {
-    applyConfigFile(nixConfDir + "/nix.conf");
+    globalConfig.applyConfigFile(settings.nixConfDir + "/nix.conf");
 
     /* We only want to send overrides to the daemon, i.e. stuff from
        ~/.nix/nix.conf or the command line. */
-    resetOverriden();
+    globalConfig.resetOverriden();
 
-    applyConfigFile(getConfigDir() + "/nix/nix.conf");
-}
-
-void Settings::set(const string & name, const string & value)
-{
-    Config::set(name, value);
+    globalConfig.applyConfigFile(getConfigDir() + "/nix/nix.conf");
 }
 
 unsigned int Settings::getDefaultCores()
@@ -162,23 +158,11 @@ void initPlugins()
                 throw Error("could not dynamically open plugin file '%s': %s", file, dlerror());
         }
     }
-    /* We handle settings registrations here, since plugins can add settings */
-    if (RegisterSetting::settingRegistrations) {
-        for (auto & registration : *RegisterSetting::settingRegistrations)
-            settings.addSetting(registration);
-        delete RegisterSetting::settingRegistrations;
-    }
-    settings.handleUnknownSettings();
+
+    /* Since plugins can add settings, try to re-apply previously
+       unknown settings. */
+    globalConfig.reapplyUnknownSettings();
+    globalConfig.warnUnknownSettings();
 }
 
-RegisterSetting::SettingRegistrations * RegisterSetting::settingRegistrations;
-
-RegisterSetting::RegisterSetting(AbstractSetting * s)
-{
-    if (!settingRegistrations)
-        settingRegistrations = new SettingRegistrations;
-    settingRegistrations->emplace_back(s);
-}
-
-
 }
diff --git a/src/libstore/globals.hh b/src/libstore/globals.hh
index 9360096a..e8d95aed 100644
--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@@ -13,26 +13,6 @@ namespace nix {
 
 typedef enum { smEnabled, smRelaxed, smDisabled } SandboxMode;
 
-extern bool useCaseHack; // FIXME
-
-struct CaseHackSetting : public BaseSetting<bool>
-{
-    CaseHackSetting(Config * options,
-        const std::string & name,
-        const std::string & description,
-        const std::set<std::string> & aliases = {})
-        : BaseSetting<bool>(useCaseHack, name, description, aliases)
-    {
-        options->addSetting(this);
-    }
-
-    void set(const std::string & str) override
-    {
-        BaseSetting<bool>::set(str);
-        nix::useCaseHack = value;
-    }
-};
-
 struct MaxBuildJobsSetting : public BaseSetting<unsigned int>
 {
     MaxBuildJobsSetting(Config * options,
@@ -56,10 +36,6 @@ public:
 
     Settings();
 
-    void loadConfFile();
-
-    void set(const string & name, const string & value);
-
     Path nixPrefix;
 
     /* The directory where we store sources and derived files. */
@@ -353,9 +329,6 @@ public:
     Setting<bool> enableImportFromDerivation{this, true, "allow-import-from-derivation",
         "Whether the evaluator allows importing the result of a derivation."};
 
-    CaseHackSetting useCaseHack{this, "use-case-hack",
-        "Whether to enable a Darwin-specific hack for dealing with file name collisions."};
-
     Setting<unsigned long> connectTimeout{this, 0, "connect-timeout",
         "Timeout for connecting to servers during downloads. 0 means use curl's builtin default."};
 
@@ -398,15 +371,8 @@ extern Settings settings;
    anything else */
 void initPlugins();
 
+void loadConfFile();
 
 extern const string nixVersion;
 
-struct RegisterSetting
-{
-    typedef std::vector<AbstractSetting *> SettingRegistrations;
-    static SettingRegistrations * settingRegistrations;
-    RegisterSetting(AbstractSetting * s);
-};
-
-
 }
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index d5303755..a157c6c4 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -187,10 +187,11 @@ void RemoteStore::setOptions(Connection & conn)
        << settings.useSubstitutes;
 
     if (GET_PROTOCOL_MINOR(conn.daemonVersion) >= 12) {
-        auto overrides = settings.getSettings(true);
+        std::map<std::string, Config::SettingInfo> overrides;
+        globalConfig.getSettings(overrides, true);
         conn.to << overrides.size();
         for (auto & i : overrides)
-            conn.to << i.first << i.second;
+            conn.to << i.first << i.second.value;
     }
 
     conn.processStderr();
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index a8f3ae1e..49b32d11 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -849,7 +849,7 @@ ref<Store> openStore(const std::string & uri_,
     for (auto fun : *RegisterStoreImplementation::implementations) {
         auto store = fun(uri, params);
         if (store) {
-            store->handleUnknownSettings();
+            store->warnUnknownSettings();
             return ref<Store>(store);
         }
     }
diff --git a/src/libutil/archive.cc b/src/libutil/archive.cc
index 154e2d20..1be8934a 100644
--- a/src/libutil/archive.cc
+++ b/src/libutil/archive.cc
@@ -13,17 +13,25 @@
 
 #include "archive.hh"
 #include "util.hh"
-
+#include "config.hh"
 
 namespace nix {
 
+struct ArchiveSettings : Config
+{
+    Setting<bool> useCaseHack{this,
+        #if __APPLE__
+            true,
+        #else
+            false,
+        #endif
+        "use-case-hack",
+        "Whether to enable a Darwin-specific hack for dealing with file name collisions."};
+};
 
-bool useCaseHack =
-#if __APPLE__
-    true;
-#else
-    false;
-#endif
+static ArchiveSettings archiveSettings;
+
+static GlobalConfig::Register r1(&archiveSettings);
 
 const std::string narVersionMagic1 = "nix-archive-1";
 
@@ -78,7 +86,7 @@ static void dump(const Path & path, Sink & sink, PathFilter & filter)
            the case hack applied by restorePath(). */
         std::map<string, string> unhacked;
         for (auto & i : readDirectory(path))
-            if (useCaseHack) {
+            if (archiveSettings.useCaseHack) {
                 string name(i.name);
                 size_t pos = i.name.find(caseHackSuffix);
                 if (pos != string::npos) {
@@ -243,7 +251,7 @@ static void parse(ParseSink & sink, Source & source, const Path & path)
                     if (name <= prevName)
                         throw Error("NAR directory is not sorted");
                     prevName = name;
-                    if (useCaseHack) {
+                    if (archiveSettings.useCaseHack) {
                         auto i = names.find(name);
                         if (i != names.end()) {
                             debug(format("case collision between '%1%' and '%2%'") % i->first % name);
diff --git a/src/libutil/archive.hh b/src/libutil/archive.hh
index 7a0e688e..25be426c 100644
--- a/src/libutil/archive.hh
+++ b/src/libutil/archive.hh
@@ -78,10 +78,6 @@ void restorePath(const Path & path, Source & source);
 void copyNAR(Source & source, Sink & sink);
 
 
-// FIXME: global variables are bad m'kay.
-extern bool useCaseHack;
-
-
 extern const std::string narVersionMagic1;
 
 
diff --git a/src/libutil/config.cc b/src/libutil/config.cc
index ce6858f0..9023cb1b 100644
--- a/src/libutil/config.cc
+++ b/src/libutil/config.cc
@@ -4,15 +4,13 @@
 
 namespace nix {
 
-void Config::set(const std::string & name, const std::string & value)
+bool Config::set(const std::string & name, const std::string & value)
 {
     auto i = _settings.find(name);
-    if (i == _settings.end()) {
-        extras.emplace(name, value);
-    } else {
-        i->second.setting->set(value);
-        i->second.setting->overriden = true;
-    }
+    if (i == _settings.end()) return false;
+    i->second.setting->set(value);
+    i->second.setting->overriden = true;
+    return true;
 }
 
 void Config::addSetting(AbstractSetting * setting)
@@ -23,46 +21,51 @@ void Config::addSetting(AbstractSetting * setting)
 
     bool set = false;
 
-    auto i = extras.find(setting->name);
-    if (i != extras.end()) {
+    auto i = unknownSettings.find(setting->name);
+    if (i != unknownSettings.end()) {
         setting->set(i->second);
         setting->overriden = true;
-        extras.erase(i);
+        unknownSettings.erase(i);
         set = true;
     }
 
     for (auto & alias : setting->aliases) {
-        auto i = extras.find(alias);
-        if (i != extras.end()) {
+        auto i = unknownSettings.find(alias);
+        if (i != unknownSettings.end()) {
             if (set)
                 warn("setting '%s' is set, but it's an alias of '%s' which is also set",
                     alias, setting->name);
             else {
                 setting->set(i->second);
                 setting->overriden = true;
-                extras.erase(i);
+                unknownSettings.erase(i);
                 set = true;
             }
         }
     }
 }
 
-void Config::handleUnknownSettings()
+void AbstractConfig::warnUnknownSettings()
 {
-    for (auto & s : extras)
+    for (auto & s : unknownSettings)
         warn("unknown setting '%s'", s.first);
 }
 
-StringMap Config::getSettings(bool overridenOnly)
+void AbstractConfig::reapplyUnknownSettings()
 {
-    StringMap res;
-    for (auto & opt : _settings)
-        if (!opt.second.isAlias && (!overridenOnly || opt.second.setting->overriden))
-            res.emplace(opt.first, opt.second.setting->to_string());
-    return res;
+    auto unknownSettings2 = std::move(unknownSettings);
+    for (auto & s : unknownSettings2)
+        set(s.first, s.second);
 }
 
-void Config::applyConfigFile(const Path & path)
+void Config::getSettings(std::map<std::string, SettingInfo> & res, bool overridenOnly)
+{
+    for (auto & opt : _settings)
+        if (!opt.second.isAlias && (!overridenOnly || opt.second.setting->overriden))
+            res.emplace(opt.first, SettingInfo{opt.second.setting->to_string(), opt.second.setting->description});
+}
+
+void AbstractConfig::applyConfigFile(const Path & path)
 {
     try {
         string contents = readFile(path);
@@ -287,4 +290,49 @@ void PathSetting::set(const std::string & str)
         value = canonPath(str);
 }
 
+bool GlobalConfig::set(const std::string & name, const std::string & value)
+{
+    for (auto & config : *configRegistrations)
+        if (config->set(name, value)) return true;
+
+    unknownSettings.emplace(name, value);
+
+    return false;
+}
+
+void GlobalConfig::getSettings(std::map<std::string, SettingInfo> & res, bool overridenOnly)
+{
+    for (auto & config : *configRegistrations)
+        config->getSettings(res, overridenOnly);
+}
+
+void GlobalConfig::resetOverriden()
+{
+    for (auto & config : *configRegistrations)
+        config->resetOverriden();
+}
+
+void GlobalConfig::toJSON(JSONObject & out)
+{
+    for (auto & config : *configRegistrations)
+        config->toJSON(out);
+}
+
+void GlobalConfig::convertToArgs(Args & args, const std::string & category)
+{
+    for (auto & config : *configRegistrations)
+        config->convertToArgs(args, category);
+}
+
+GlobalConfig globalConfig;
+
+GlobalConfig::ConfigRegistrations * GlobalConfig::configRegistrations;
+
+GlobalConfig::Register::Register(Config * config)
+{
+    if (!configRegistrations)
+        configRegistrations = new ConfigRegistrations;
+    configRegistrations->emplace_back(config);
+}
+
 }
diff --git a/src/libutil/config.hh b/src/libutil/config.hh
index d2e7faf1..d86c65ff 100644
--- a/src/libutil/config.hh
+++ b/src/libutil/config.hh
@@ -12,6 +12,40 @@ class AbstractSetting;
 class JSONPlaceholder;
 class JSONObject;
 
+class AbstractConfig
+{
+protected:
+    StringMap unknownSettings;
+
+    AbstractConfig(const StringMap & initials = {})
+        : unknownSettings(initials)
+    { }
+
+public:
+
+    virtual bool set(const std::string & name, const std::string & value) = 0;
+
+    struct SettingInfo
+    {
+        std::string value;
+        std::string description;
+    };
+
+    virtual void getSettings(std::map<std::string, SettingInfo> & res, bool overridenOnly = false) = 0;
+
+    void applyConfigFile(const Path & path);
+
+    virtual void resetOverriden() = 0;
+
+    virtual void toJSON(JSONObject & out) = 0;
+
+    virtual void convertToArgs(Args & args, const std::string & category) = 0;
+
+    void warnUnknownSettings();
+
+    void reapplyUnknownSettings();
+};
+
 /* A class to simplify providing configuration settings. The typical
    use is to inherit Config and add Setting<T> members:
 
@@ -27,7 +61,7 @@ class JSONObject;
    };
 */
 
-class Config
+class Config : public AbstractConfig
 {
     friend class AbstractSetting;
 
@@ -48,31 +82,23 @@ private:
 
     Settings _settings;
 
-    StringMap extras;
-
 public:
 
-    Config(const StringMap & initials)
-        : extras(initials)
+    Config(const StringMap & initials = {})
+        : AbstractConfig(initials)
     { }
 
-    void set(const std::string & name, const std::string & value);
+    bool set(const std::string & name, const std::string & value) override;
 
     void addSetting(AbstractSetting * setting);
 
-    void handleUnknownSettings();
+    void getSettings(std::map<std::string, SettingInfo> & res, bool overridenOnly = false) override;
 
-    StringMap getSettings(bool overridenOnly = false);
+    void resetOverriden() override;
 
-    const Settings & _getSettings() { return _settings; }
+    void toJSON(JSONObject & out) override;
 
-    void applyConfigFile(const Path & path);
-
-    void resetOverriden();
-
-    void toJSON(JSONObject & out);
-
-    void convertToArgs(Args & args, const std::string & category);
+    void convertToArgs(Args & args, const std::string & category) override;
 };
 
 class AbstractSetting
@@ -209,4 +235,27 @@ public:
     void operator =(const Path & v) { this->assign(v); }
 };
 
+struct GlobalConfig : public AbstractConfig
+{
+    typedef std::vector<Config*> ConfigRegistrations;
+    static ConfigRegistrations * configRegistrations;
+
+    bool set(const std::string & name, const std::string & value) override;
+
+    void getSettings(std::map<std::string, SettingInfo> & res, bool overridenOnly = false) override;
+
+    void resetOverriden() override;
+
+    void toJSON(JSONObject & out) override;
+
+    void convertToArgs(Args & args, const std::string & category) override;
+
+    struct Register
+    {
+        Register(Config * config);
+    };
+};
+
+extern GlobalConfig globalConfig;
+
 }
diff --git a/src/nix/main.cc b/src/nix/main.cc
index bb107ec7..9cd5d21c 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -34,9 +34,10 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs
             .handler([&]() {
                 std::cout << "The following configuration options are available:\n\n";
                 Table2 tbl;
-                for (const auto & s : settings._getSettings())
-                    if (!s.second.isAlias)
-                        tbl.emplace_back(s.first, s.second.setting->description);
+                std::map<std::string, Config::SettingInfo> settings;
+                globalConfig.getSettings(settings);
+                for (const auto & s : settings)
+                    tbl.emplace_back(s.first, s.second.description);
                 printTable(std::cout, tbl);
                 throw Exit();
             });
diff --git a/src/nix/show-config.cc b/src/nix/show-config.cc
index c64b12c8..86638b50 100644
--- a/src/nix/show-config.cc
+++ b/src/nix/show-config.cc
@@ -27,10 +27,12 @@ struct CmdShowConfig : Command, MixJSON
         if (json) {
             // FIXME: use appropriate JSON types (bool, ints, etc).
             JSONObject jsonObj(std::cout);
-            settings.toJSON(jsonObj);
+            globalConfig.toJSON(jsonObj);
         } else {
-            for (auto & s : settings.getSettings())
-                std::cout << s.first + " = " + s.second + "\n";
+            std::map<std::string, Config::SettingInfo> settings;
+            globalConfig.getSettings(settings);
+            for (auto & s : settings)
+                std::cout << s.first + " = " + s.second.value + "\n";
         }
     }
 };
diff --git a/tests/plugins/plugintest.cc b/tests/plugins/plugintest.cc
index 8da15eba..c085d332 100644
--- a/tests/plugins/plugintest.cc
+++ b/tests/plugins/plugintest.cc
@@ -1,16 +1,21 @@
-#include "globals.hh"
+#include "config.hh"
 #include "primops.hh"
 
 using namespace nix;
 
-static BaseSetting<bool> settingSet{false, "setting-set",
+struct MySettings : Config
+{
+    Setting<bool> settingSet{this, false, "setting-set",
         "Whether the plugin-defined setting was set"};
+};
 
-static RegisterSetting rs(&settingSet);
+MySettings mySettings;
+
+static GlobalConfig::Register rs(&mySettings);
 
 static void prim_anotherNull (EvalState & state, const Pos & pos, Value ** args, Value & v)
 {
-    if (settingSet)
+    if (mySettings.settingSet)
         mkNull(v);
     else
         mkBool(v, false);