diff --git a/src/slic3r/GUI/GUI_App.cpp b/src/slic3r/GUI/GUI_App.cpp
index c4014bd4b6..dcc0c44178 100644
--- a/src/slic3r/GUI/GUI_App.cpp
+++ b/src/slic3r/GUI/GUI_App.cpp
@@ -684,15 +684,16 @@ bool GUI_App::select_language()
 	// Try to load a new language.
     if (index != -1 && (init_selection == -1 || init_selection != index)) {
     	const wxLanguageInfo *new_language_info = language_infos[index];
-        if (new_language_info == m_language_info_best || new_language_info == m_language_info_system) {
-        	// The newly selected profile matches user's default profile exactly. That's great.
-        } else if (m_language_info_best != nullptr && new_language_info->CanonicalName.BeforeFirst('_') == m_language_info_best->CanonicalName.BeforeFirst('_'))
-    		new_language_info = m_language_info_best;
-    	else if (m_language_info_system != nullptr && new_language_info->CanonicalName.BeforeFirst('_') == m_language_info_system->CanonicalName.BeforeFirst('_'))
-            new_language_info = m_language_info_system;
     	if (this->load_language(new_language_info->CanonicalName, false)) {
 			// Save language at application config.
-			app_config->set("translation_language", m_wxLocale->GetCanonicalName().ToUTF8().data());
+            // Which language to save as the selected dictionary language?
+            // 1) Hopefully the language set to wxTranslations by this->load_language(), but that API is weird and we don't want to rely on its
+            //    stability in the future:
+            //    wxTranslations::Get()->GetBestTranslation(SLIC3R_APP_KEY, wxLANGUAGE_ENGLISH);
+            // 2) Current locale language may not match the dictionary name, see GH issue #3901
+            //    m_wxLocale->GetCanonicalName()
+            // 3) new_language_info->CanonicalName is a safe bet. It points to a valid dictionary name.
+			app_config->set("translation_language", new_language_info->CanonicalName.ToUTF8().data());            
 			app_config->save();
     		return true;
     	}
@@ -721,7 +722,6 @@ bool GUI_App::load_language(wxString language, bool initial)
 	        	BOOST_LOG_TRIVIAL(trace) << boost::format("System language detected (user locales and such): %1%") % m_language_info_system->CanonicalName.ToUTF8().data();
 	        }
 		}
-#if defined(__WXMSW__) || defined(__WXOSX__)
         {
 	    	// Allocating a temporary locale will switch the default wxTranslations to its internal wxTranslations instance.
 	    	wxLocale temp_locale;
@@ -738,7 +738,6 @@ bool GUI_App::load_language(wxString language, bool initial)
 	        	BOOST_LOG_TRIVIAL(trace) << boost::format("Best translation language detected (may be different from user locales): %1%") % m_language_info_best->CanonicalName.ToUTF8().data();
 			}
 		}
-#endif
     }
 
 	const wxLanguageInfo *language_info = language.empty() ? nullptr : wxLocale::FindLanguageInfo(language);
@@ -754,6 +753,7 @@ bool GUI_App::load_language(wxString language, bool initial)
 	}
 
     if (language_info == nullptr) {
+        // PrusaSlicer does not support the Right to Left languages yet.
         if (m_language_info_system != nullptr && m_language_info_system->LayoutDirection != wxLayout_RightToLeft)
             language_info = m_language_info_system;
         if (m_language_info_best != nullptr && m_language_info_best->LayoutDirection != wxLayout_RightToLeft)
@@ -772,6 +772,16 @@ bool GUI_App::load_language(wxString language, bool initial)
 		BOOST_LOG_TRIVIAL(trace) << "Using Czech dictionaries for Slovak language";
     }
 
+    // Select language for locales. This language may be different from the language of the dictionary.
+    if (language_info == m_language_info_best || language_info == m_language_info_system) {
+        // The current language matches user's default profile exactly. That's great.
+    } else if (m_language_info_best != nullptr && language_info->CanonicalName.BeforeFirst('_') == m_language_info_best->CanonicalName.BeforeFirst('_')) {
+        // Use whatever the operating system recommends, if it the language code of the dictionary matches the recommended language.
+        // This allows a Swiss guy to use a German dictionary without forcing him to German locales.
+        language_info = m_language_info_best;
+    } else if (m_language_info_system != nullptr && language_info->CanonicalName.BeforeFirst('_') == m_language_info_system->CanonicalName.BeforeFirst('_'))
+        language_info = m_language_info_system;
+
     if (! wxLocale::IsAvailable(language_info->Language)) {
     	// Loading the language dictionary failed.
     	wxString message = "Switching PrusaSlicer to language " + language_info->CanonicalName + " failed.";