diff --git a/rtdata/themes/RawTherapee.css b/rtdata/themes/RawTherapee-GTK3-20_.css
similarity index 100%
rename from rtdata/themes/RawTherapee.css
rename to rtdata/themes/RawTherapee-GTK3-20_.css
diff --git a/rtdata/themes/RawTherapee-GTK3-_19.css b/rtdata/themes/RawTherapee-GTK3-_19.css
new file mode 100644
index 000000000..e6eac9793
--- /dev/null
+++ b/rtdata/themes/RawTherapee-GTK3-_19.css
@@ -0,0 +1,448 @@
+/*
+  This file is part of RawTherapee.
+
+  Copyright (c) 2015 DrSlony
+  Copyright (c) 2016 Hombre
+
+  RawTherapee 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 3 of the License, or
+  (at your option) any later version.
+
+  RawTherapee is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with RawTherapee.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+* {
+    color: #AAAAAA;
+}
+
+.view:selected {
+    color: #262626;
+    background-color: #AAAAAA
+}
+
+/* The Places and Dir browser panels */
+.view {
+    background-color: #262626;
+}
+/* The headers of these panels */
+.view .button {
+    background-color: #363636;
+    padding: 2px;
+}
+
+.plainback {
+    background-color: #404040;
+}
+
+GtkBox {
+    border-width: 0;
+    border-style: none;
+    border-radius: 0;
+    margin: 0;
+	padding: 0;
+}
+
+GtkGrid {
+    margin: 2px;
+    padding: 0;
+    border-width: 0;
+    border-style: none;
+    border-radius: 0;
+}
+
+/* Affects all frames except in the toolbox */
+GtkFrame {
+    border-width: 0;
+    border-color: #303030;
+    border-radius: 0;
+    border-style: solid;
+    /*border-style: none none none solid;*/
+    padding: 4px;
+}
+
+GtkFrame > GtkLabel {
+    color: #D8D8D8;
+}
+
+#FileBrowser {
+    padding: 10px;
+    margin: 10px;
+}
+
+/* Frames in Preferences */
+#PrefNotebook GtkFrame {
+    background-color: #3B3B3B;
+    border: 1px solid #505050;
+    border-radius: 4px;
+}
+
+/* Frames in the toolbox. Not MyExpander frames. */
+GtkEventBox .frame {
+    border-color: #565656;
+}
+
+/*.EditorTopPanel .button, .ToolBarPanelFileBrowser .button, .EditorZoomPanel .button {*/
+.button {
+     padding: 1px;
+     margin: 1px;
+}
+
+/* Adjusters */
+.text-button {
+    padding: 0;
+}
+
+/* Any text-button which is a real button, unlike Slider label */
+.text-button.button {
+    padding: 4px;
+}
+
+.separator {
+    color: #363636;
+}
+
+GtkProgressBar {
+    -GtkProgressBar-min-vertical-bar-width: 10;
+    -GtkProgressBar-min-horizontal-bar-height: 10;
+}
+
+GtkDrawingArea {
+    border-radius: 0;
+    background-color: #363636;
+    border: 1px solid #252525;
+}
+
+GtkDrawingArea:selected {
+    background-color: #565656;
+    border-radius: 10px;
+}
+
+GtkImage {
+    padding: 1px;
+}
+
+/* Vertical group of buttons in 1 column */
+GtkButton.Top {
+    border-radius: 10px 4px 0 0;
+    border-style: solid solid none solid;
+    margin-bottom: 0;
+}
+GtkButton.MiddleV {
+    border-radius: 0;
+    border-style: none solid none solid;
+    margin-top: 0;
+    margin-bottom: 0;
+}
+GtkButton.Bottom {
+    border-radius: 0 0 4px 4px;
+    border-style: none solid solid solid;
+    margin-top: 0;
+}
+/* end */
+
+/* Horizontal group of buttons in 1 row */
+GtkButton.Left {
+    border-radius: 4px 0 0 4px;
+    border-style: solid none solid solid;
+    margin-right: 0;
+}
+GtkButton.MiddleH {
+    border-radius: 0;
+    border-style: solid none solid none;
+    margin-left: 0;
+    margin-right: 0;
+}
+GtkButton.Right {
+    border-radius: 0 4px 4px 0;
+    border-style: solid solid solid none;
+    margin-left: 0;
+}
+/* end */
+
+/* [1.23[-][+]] */
+GtkEntry, GtkSpinButton {
+    padding: 1px;
+    background-color: #262626;
+}
+
+GtkEntry:insensitive, GtkSpinButton:insensitive {
+    background-color: #363636;
+}
+
+GtkEntry:hover, GtkSpinButton:hover {
+    background-color: #565656;
+}
+
+GtkEntry:selected {
+    color: #262626;
+    background-color: #AAAAAA;
+}
+
+/* Context menus */
+GtkMenu {
+    background-color: #262626;
+    color: #909090;
+}
+
+/* Context menu item */
+.menuitem {
+    padding: 2px;
+}
+
+#MyExpander {
+    margin: 10px;
+    padding: 5px;
+}
+
+/* Tool background */
+#ExpanderBox {
+    background-color: #363636;
+    border-width: 1px;
+    border-style: solid;
+    border-radius: 4px;
+    border-color: #252525;
+    margin: 9px;
+    padding: 4px;
+}
+
+#ExpanderBox GtkDrawingArea {
+    background-color: #363636;
+}
+
+#ExpanderBox GtkFrame {
+    background-color: #3B3B3B;
+    border-style: solid;
+    border-width: 1px;
+    border-radius: 4px;
+    border-color: #313131;
+    margin: 3px;
+    padding: 2px;
+}
+
+#ExpanderBox GtkFrame GtkDrawingArea {
+    background-color: #3B3B3B;
+}
+
+#ExpanderBox GtkFrame GtkFrame {
+    background-color: #414141;
+    border: 1px solid #373737;
+    border-radius: 4px;
+    margin: 3px;
+    padding: 2px;
+}
+
+#ExpanderBox GtkFrame GtkFrame GtkDrawingArea {
+    background-color: #414141;
+}
+
+/* Sub-tool (MyExpander) background */
+#ExpanderBox2 {
+    background-color: #3B3B3B;
+    border: 1px solid #2A2A2A;
+    border-radius: 4px;
+    margin: 9px;
+    padding: 4px;
+}
+
+#ExpanderBox2 GtkDrawingArea {
+    background-color: #3B3B3B;
+}
+
+#ExpanderBox2 GtkFrame {
+    background-color: #414141;
+    border: 1px solid #373737;
+    border-radius: 4px;
+    margin: 3px;
+    padding: 2px;
+}
+
+#ExpanderBox2 GtkFrame GtkDrawingArea {
+    background-color: #414141;
+}
+
+#ExpanderBox2 GtkFrame GtkFrame {
+    background-color: #474747;
+    border: 1px solid #3D3D3D;
+    border-radius: 4px;
+    margin: 3px;
+    padding: 2px;
+}
+
+#ExpanderBox2 GtkFrame GtkFrame GtkDrawingArea {
+    background-color: #474747;
+}
+
+#MyExpanderTitle {
+    margin: 5px;
+    padding: 3px 1px 3px 1px;
+    font-size: 120%;
+}
+#MyExpanderTitle GtkLabel {
+    color: #CCCCCC;
+}
+#MyExpanderTitle:hover {
+    background-color: #202020;
+}
+#MyExpanderTitle GtkEventBox:hover GtkImage {
+    background-color: #202020;
+    border-radius: 3px;
+}
+#MyExpanderTitle:hover GtkLabel {
+    color: #D8D8D8;
+}
+
+#ExpanderBox2 GtkSeparator, #ExpanderBox3 GtkSeparator {
+    color: #292929;
+}
+
+/* Editor tab button */
+#MainNotebook > GtkGrid GtkLabel, #MainNotebook > GtkGrid GtkImage  {
+    /* OK */
+    padding: 1px;
+}
+
+/* File Browser right side tabs - Toolbox, Inspector, Fast Export, Filter */
+GtkNotebook tab {
+    background-color: #383838;
+    border-width: 1px;
+    border-style: none;
+    border-color: #262626;
+    border-radius: 0;
+    padding: 3px;
+}
+
+GtkNotebook tab:hover {
+    background-color: #505050;
+}
+
+GtkNotebook tab:active {
+    border-width: 5px;
+    border-color: #989898;
+}
+
+/* Get rid of shitty notebook header shadow */
+GtkNotebook.top tab {
+    border-bottom-style: solid;
+    padding-bottom: 8px;
+}
+GtkNotebook.right tab {
+    border-left-style: solid;
+    padding-left: 8px;
+}
+GtkNotebook.bottom tab {
+    border-top-style: solid;
+    padding-top: 8px;
+}
+GtkNotebook.left tab {
+    border-right-style: solid;
+    padding-right: 8px;
+}
+
+/* Get rid of notebook frame border - too many borders */
+GtkNotebook.top.header, GtkNotebook.right.header, GtkNotebook.bottom.header, GtkNotebook.left.header {
+    box-shadow: none;
+    border-width: 1px;
+    border-color: #262626;
+    border-style: none;
+    border-radius: 0;
+    background-color: #383838;
+    padding: 0;
+}
+/* Get rid of notebook header border - too many borders */
+GtkNotebook.top.header {
+    /* OK */
+    border-bottom-style: solid;
+}
+GtkNotebook.right.header {
+    /* OK */
+    border-left-style: solid;
+}
+GtkNotebook.bottom.header {
+    /* OK */
+    border-top-style: solid;
+}
+GtkNotebook.left.header {
+    /* OK */
+    border-right-style: solid;
+}
+GtkNotebook.frame {
+    /* OK */
+    border-radius: 0;
+    border-style: none;
+}
+
+/* Pad notebooks, makes the other borders look nicer */
+GtkNotebook {
+    /* OK */
+    background-color: #484848;
+    padding: 0;
+}
+
+
+#MainNotebook.header {
+    /* OK */
+    background-color: #2A2A2A;
+}
+#MainNotebook > tab {
+    /* OK */
+    background-color: #2A2A2A;
+}
+#MainNotebook > tab:hover {
+    /* OK */
+    background-color: #505050;
+}
+#MainNotebook > tab:active {
+    /* OK */
+    border-color: #989898;
+}
+
+#RightNotebook.header {
+    /* OK */
+    background-color: #2A2A2A;
+}
+#RightNotebook > tab {
+    /* OK */
+    background-color: #2A2A2A;
+}
+#RightNotebook > tab:hover {
+    /* OK */
+    background-color: #505050;
+}
+#RightNotebook > tab:active {
+    /* OK */
+    border-color: #989898;
+}
+
+
+/* All tool panels have a frame except for Meta which unlike the rest is a notebook itself.
+ * So we use CSS to make it look like a frame. */
+#MetaPanelNotebook.frame {
+    border: 1px solid #262626;
+    border-bottom-left-radius: 4px;
+    border-bottom-right-radius: 4px;
+    border-top-left-radius: 0;
+    border-top-right-radius: 0;
+    border-top-width: 0;
+}
+
+#MetaPanelNotebook.header {
+    border: 1px solid #262626;
+    border-bottom-left-radius: 0;
+    border-bottom-right-radius: 0;
+    border-top-left-radius: 4px;
+    border-top-right-radius: 4px;
+    border-bottom-width: 0;
+    padding: 5px;
+    margin: 5px;
+}
+
+.tooltip {
+    padding: 0;
+}
diff --git a/rtgui/main.cc b/rtgui/main.cc
index 1933939f8..c984b4632 100644
--- a/rtgui/main.cc
+++ b/rtgui/main.cc
@@ -56,7 +56,6 @@ Glib::ustring creditsPath;
 Glib::ustring licensePath;
 Glib::ustring argv1;
 bool simpleEditor;
-Glib::RefPtr<Gtk::CssProvider> cssForced;
 Glib::RefPtr<Gtk::CssProvider> cssRT;
 //Glib::Threads::Thread* mainThread;
 
@@ -313,7 +312,13 @@ int main(int argc, char **argv)
 
         Glib::ustring filename = Glib::build_filename(argv0, "themes", options.theme + ".css");
         if (!Glib::file_test(filename, Glib::FILE_TEST_EXISTS)) {
-            options.theme = "RawTherapee";
+            options.theme = "RawTherapee-GTK";
+            // We're not testing GTK_MAJOR_VERSION == 3 here, since this branch requires Gtk3 only
+            if (GTK_MINOR_VERSION < 20) {
+                options.theme = options.theme + "3-_19";
+            } else {
+                options.theme = options.theme + "3-20_";
+            }
             filename = Glib::build_filename(argv0, "themes", options.theme + ".css");
         }
         cssRT = Gtk::CssProvider::create();
diff --git a/rtgui/preferences.cc b/rtgui/preferences.cc
index 2be4cecd3..efc5d3972 100644
--- a/rtgui/preferences.cc
+++ b/rtgui/preferences.cc
@@ -41,6 +41,8 @@ Preferences::Preferences  (RTWindow *rtwindow)
     , parent (rtwindow)
     , splash (nullptr)
 {
+    regex = Glib::Regex::create("^(.+)-GTK3-(\\d{1,2})?_(\\d{1,2})?\\.css$", Glib::RegexCompileFlags::REGEX_CASELESS);
+
     moptions.copyFrom (&options);
 
     /*
@@ -100,6 +102,19 @@ Preferences::~Preferences ()
     options.preferencesHeight = get_height();
 }
 
+int Preferences::getThemeRowNumber(Glib::ustring& longThemeFName)
+{
+
+    if (regex->match(longThemeFName + ".css", matchInfo)) {
+        for (size_t i=0 ; i<themeFNames.size(); ++i) {
+            if (themeFNames.at(i).longFName == longThemeFName) {
+                return (int)i;
+            }
+        }
+    }
+    return -1;
+}
+
 Gtk::Widget* Preferences::getBatchProcPanel ()
 {
 
@@ -893,11 +908,10 @@ Gtk::Widget* Preferences::getGeneralPanel ()
     setExpandAlignProperties(theme, false, false, Gtk::ALIGN_START, Gtk::ALIGN_BASELINE);
 
     theme->set_active (0);
-    std::vector<Glib::ustring> themes;
-    parseDir (argv0 + "/themes", themes, ".css");
+    parseThemeDir (Glib::build_filename(argv0, "themes"));
 
-    for (size_t i = 0; i < themes.size(); i++) {
-        theme->append (themes[i]);
+    for (size_t i = 0; i < themeFNames.size(); i++) {
+        theme->append (themeFNames.at(i).shortFName);
     }
 
     themeGrid->attach_next_to(*themelab, Gtk::POS_LEFT, 1, 1);
@@ -1337,6 +1351,59 @@ void Preferences::parseDir (Glib::ustring dirname, std::vector<Glib::ustring>& i
     delete dir;
 }
 
+void Preferences::parseThemeDir (Glib::ustring dirname)
+{
+
+    if (dirname.empty()) {
+        return;
+    }
+
+    // process directory
+    Glib::Dir* dir = nullptr;
+
+    try {
+        dir = new Glib::Dir (dirname);
+    } catch (const Glib::Error& e) {
+        return;
+    }
+
+    for (Glib::DirIterator i = dir->begin(); i != dir->end(); ++i) {
+        Glib::ustring fname = Glib::build_filename(dirname, *i);
+        Glib::ustring sname = *i;
+
+        bool keepIt = false;
+
+        // ignore directories and filter out unsupported theme
+        if (regex->match(sname, matchInfo) && !Glib::file_test (fname, Glib::FILE_TEST_IS_DIR) && sname.size() >= 4) {
+            Glib::ustring fname2 = matchInfo.fetch(1);
+            Glib::ustring minMinor = matchInfo.fetch(2);
+            Glib::ustring maxMinor = matchInfo.fetch(3);
+
+            if (!minMinor.empty()) {
+                guint64 minMinorVal = g_ascii_strtoll(minMinor.c_str(), 0, 0);
+                if ((guint64)GTK_MINOR_VERSION >= minMinorVal) {
+                    keepIt = true;
+                }
+            }
+            if (!maxMinor.empty()) {
+                guint64 maxMinorVal = g_ascii_strtoll(maxMinor.c_str(), 0, 0);
+                if ((guint64)GTK_MINOR_VERSION <= maxMinorVal) {
+                    keepIt = true;
+                }
+            }
+            if (keepIt) {
+                themeFNames.push_back(ThemeFilename(matchInfo.fetch(1), sname.substr(0, sname.size() - 4)));
+            }
+        }
+    }
+    std::sort(themeFNames.begin(), themeFNames.end(), [] (const ThemeFilename& firstDir, const ThemeFilename& secondDir)
+            {
+                return firstDir.longFName < secondDir.longFName;
+            });
+
+    delete dir;
+}
+
 void Preferences::storePreferences ()
 {
 
@@ -1369,7 +1436,7 @@ void Preferences::storePreferences ()
     moptions.shadowThreshold = (int)shThresh->get_value ();
     moptions.language        = languages->get_active_text ();
     moptions.languageAutoDetect = ckbLangAutoDetect->get_active ();
-    moptions.theme           = theme->get_active_text ();
+    moptions.theme           = themeFNames.at(theme->get_active_row_number ()).longFName;
 
     Gdk::RGBA cropCol = butCropCol->get_rgba();
     moptions.cutOverlayBrush[0] = cropCol.get_red();
@@ -1585,7 +1652,8 @@ void Preferences::fillPreferences ()
     ckbHistogramWorking->set_active (moptions.rtSettings.HistogramWorking);
     languages->set_active_text (moptions.language);
     ckbLangAutoDetect->set_active (moptions.languageAutoDetect);
-    theme->set_active_text (moptions.theme);
+    int themeNbr = getThemeRowNumber(moptions.theme);
+    theme->set_active (themeNbr==-1 ? 0 : themeNbr);
 
     Gdk::RGBA cropCol;
     cropCol.set_rgba(moptions.cutOverlayBrush[0], moptions.cutOverlayBrush[1], moptions.cutOverlayBrush[2]);
@@ -1783,7 +1851,7 @@ void Preferences::okPressed ()
 void Preferences::cancelPressed ()
 {
     // set the initial theme back
-    if (theme->get_active_text() != options.theme) {
+    if (themeFNames.at(theme->get_active_row_number ()).longFName != options.theme) {
         RTImage::setPaths(options);
         RTImage::updateImages();
         switchThemeTo(options.theme);
@@ -1830,10 +1898,10 @@ void Preferences::aboutPressed ()
 void Preferences::themeChanged ()
 {
 
-    moptions.theme = theme->get_active_text ();
+    moptions.theme = themeFNames.at(theme->get_active_row_number ()).longFName;
     RTImage::setPaths(moptions);
     RTImage::updateImages();
-    switchThemeTo(theme->get_active_text ());
+    switchThemeTo(moptions.theme);
 }
 
 void Preferences::forRAWComboChanged ()
@@ -1961,10 +2029,12 @@ void Preferences::restoreValue()
 void Preferences::switchThemeTo(Glib::ustring newTheme)
 {
 
-    Glib::ustring filename(argv0 + "/themes/" + newTheme + ".css");
+    Glib::ustring filename(Glib::build_filename(argv0, "themes", newTheme + ".css"));
 
     if (!css) {
         css = Gtk::CssProvider::create();
+        Glib::RefPtr<Gdk::Screen> screen = Gdk::Screen::get_default();
+        Gtk::StyleContext::add_provider_for_screen(screen, css, GTK_STYLE_PROVIDER_PRIORITY_USER);
     }
 
     try {
diff --git a/rtgui/preferences.h b/rtgui/preferences.h
index a1706f954..749b9669b 100644
--- a/rtgui/preferences.h
+++ b/rtgui/preferences.h
@@ -60,11 +60,21 @@ class Preferences : public Gtk::Dialog, public ProfileStoreListener
             add(addsetid);
         }
     };
+
+    class ThemeFilename
+    {
+    public:
+        Glib::ustring shortFName;
+        Glib::ustring longFName;
+
+        ThemeFilename (Glib::ustring sfname, Glib::ustring lfname) : shortFName(sfname), longFName(lfname) {}
+    };
+
     Glib::RefPtr<Gtk::TreeStore> behModel;
     BehavColumns behavColumns;
-
-
-protected:
+    std::vector<ThemeFilename> themeFNames;
+    Glib::RefPtr<Glib::Regex> regex;
+    Glib::MatchInfo matchInfo;
     Splash* splash;
     ProfileStoreComboBox* rprofiles;
     Gtk::TreeIter currRawRow; // :)
@@ -198,6 +208,7 @@ protected:
     void fillPreferences ();
     void storePreferences ();
     void parseDir       (Glib::ustring dirname, std::vector<Glib::ustring>& items, Glib::ustring ext);
+    void parseThemeDir  (Glib::ustring dirname);
     void updateDFinfos ();
     void updateFFinfos ();
     void workflowUpdate();
@@ -210,6 +221,8 @@ protected:
     void switchThemeTo (Glib::ustring newTheme);
     bool splashClosed(GdkEventAny* event);
 
+    int getThemeRowNumber(Glib::ustring& longThemeFName);
+
     void appendBehavList (Gtk::TreeModel::iterator& parent, Glib::ustring label, int id, bool set);
 
     Gtk::Widget* getProcParamsPanel ();