diff --git a/rtgui/filmsimulation.cc b/rtgui/filmsimulation.cc
index a1471f970..716b686e9 100644
--- a/rtgui/filmsimulation.cc
+++ b/rtgui/filmsimulation.cc
@@ -1,3 +1,6 @@
+#include <map>
+#include <set>
+
 #include "filmsimulation.h"
 
 #include <chrono>
@@ -56,8 +59,6 @@ bool notifySlowParseDir (const std::chrono::system_clock::time_point& startedAt)
 
 }
 
-typedef std::vector<Glib::ustring> Strings;
-
 FilmSimulation::FilmSimulation()
     :   FoldableToolPanel( this, "filmsimulation", M("TP_FILMSIMULATION_LABEL"), false, true )
 {
@@ -216,13 +217,28 @@ int ClutComboBox::fillFromDir (const Glib::ustring& path)
     return result;
 }
 
-int ClutComboBox::parseDir (const Glib::ustring& path)
+int ClutComboBox::parseDir(const Glib::ustring& path)
 {
-    if (path.empty () || !Glib::file_test (path, Glib::FILE_TEST_IS_DIR)) {
+    if (path.empty() || !Glib::file_test(path, Glib::FILE_TEST_IS_DIR)) {
         return 0;
     }
 
-    const auto startedAt = std::chrono::system_clock::now ();
+    const auto sorted_dir_dirs = [](const Glib::ustring& path) -> std::map<std::string, std::string>
+        {
+            std::map<std::string, std::string> res;
+
+            for (const auto& dir : Glib::Dir(path)) {
+                const std::string full_path = Glib::build_filename(path, dir);
+
+                if (Glib::file_test(full_path, Glib::FILE_TEST_IS_DIR)) {
+                    res.emplace(dir, full_path);
+                }
+            }
+
+            return res;
+        };
+
+    const auto startedAt = std::chrono::system_clock::now();
 
     // Build menu of limited directory structure using breadth-first search
     using Dirs = std::vector<std::pair<Glib::ustring, Gtk::TreeModel::Row>>;
@@ -232,89 +248,77 @@ int ClutComboBox::parseDir (const Glib::ustring& path)
         Dirs currDirs;
         Dirs nextDirs;
 
-        currDirs.emplace_back (path, Gtk::TreeModel::Row ());
-
-        while (!currDirs.empty ()) {
+        currDirs.emplace_back(path, Gtk::TreeModel::Row());
 
+        while (!currDirs.empty()) {
             for (auto& dir : currDirs) {
-
                 const auto& path = dir.first;
                 const auto& row = dir.second;
 
                 try {
-                    for (const auto& entry : Glib::Dir (path)) {
+                    for (const auto& entry : sorted_dir_dirs(path)) {
+                        auto newRow = row ? *m_model->append(row.children()) : *m_model->append();
+                        newRow[m_columns.label] = entry.first;
 
-                        const auto entryPath = Glib::build_filename (path, entry);
-
-                        if (!Glib::file_test (entryPath, Glib::FILE_TEST_IS_DIR)) {
-                            continue;
-                        }
-
-                        auto newRow = row ? *m_model->append (row.children ()) : *m_model->append ();
-                        newRow[m_columns.label] = entry;
-
-                        nextDirs.emplace_back (entryPath, newRow);
+                        nextDirs.emplace_back(entry.second, newRow);
                     }
                 } catch (Glib::Exception&) {}
 
-                dirs.push_back (std::move (dir));
+                dirs.push_back(std::move(dir));
 
-                if (!notifySlowParseDir (startedAt)) {
-                    m_model->clear ();
+                if (!notifySlowParseDir(startedAt)) {
+                    m_model->clear();
                     return 0;
                 }
             }
 
-            currDirs.clear ();
-            currDirs.swap (nextDirs);
+            currDirs.clear();
+            currDirs.swap(nextDirs);
         }
     }
 
     // Fill menu structure with CLUT files
-    Strings entries;
+    std::set<Glib::ustring> entries;
 
-    auto fileCount = 0;
+    unsigned long fileCount = 0;
 
     for (const auto& dir : dirs) {
-
         const auto& path = dir.first;
         const auto& row = dir.second;
 
-        entries.clear ();
+        entries.clear();
 
         try {
-            for (const auto& entry : Glib::Dir (path)) {
+            for (const auto& entry : Glib::Dir(path)) {
+                const auto entryPath = Glib::build_filename(path, entry);
 
-                const auto entryPath = Glib::build_filename (path, entry);
-
-                if (!Glib::file_test (entryPath, Glib::FILE_TEST_IS_REGULAR)) {
+                if (!Glib::file_test(entryPath, Glib::FILE_TEST_IS_REGULAR)) {
                     continue;
                 }
 
-                entries.push_back (entryPath);
+                entries.insert(entryPath);
             }
         } catch (Glib::Exception&) {}
 
-        std::sort (entries.begin (), entries.end ());
-
         for (const auto& entry : entries) {
-
-            Glib::ustring name, extension, profileName;
+            Glib::ustring name;
+            Glib::ustring extension;
+            Glib::ustring profileName;
             HaldCLUT::splitClutFilename (entry, name, extension, profileName);
 
-            extension = extension.casefold ();
-            if (extension.compare ("tif") != 0 && extension.compare ("png") != 0) {
+            extension = extension.casefold();
+            if (extension.compare("tif") != 0 && extension.compare("png") != 0) {
                 continue;
             }
 
-            auto newRow = row ? *m_model->append (row.children ()) : *m_model->append ();
+            auto newRow = row ? *m_model->append(row.children()) : *m_model->append();
             newRow[m_columns.label] = name;
             newRow[m_columns.clutFilename] = entry;
 
             ++fileCount;
 
-            if (!notifySlowParseDir (startedAt)) {
-                m_model->clear ();
+            if (!notifySlowParseDir(startedAt)) {
+                m_model->clear();
                 return 0;
             }
         }